GO Cellular Component Annotations 2023 Dataset

Description curated annotations of genes with cellular components
Measurement association by literature curation
Association gene-cellular component associations from curated gene annotations
Category structural or functional annotations
Resource Gene Ontology
Citation(s)
Last Updated 2015 Mar 31
Stats
  1. 11089 genes
  2. 926 cellular components
  3. 41883 gene-cellular component associations

Data Access

API
Script

Visualizations

  • Gene Attribute

  • Gene Similarity

  • Attribute Similarity

  • UMAP

cellular component Gene Sets

926 sets of proteins localized to cellular components from the curated GO Cellular Component Annotations 2023 dataset.

Gene Set Description
7SK snRNP
9+0 non-motile cilium
9+2 motile cilium
90S preribosome A large ribonucleoprotein complex considered to be the earliest preribosomal complex. In S. cerevisiae, it has a size of 90S and consists of the 35S pre-rRNA, early-associating ribosomal proteins most of which are part of the small ribosomal subunit, the U3 snoRNA and associated proteins.
acetylcholine-gated channel complex A homo- or hetero-pentameric protein complex that forms a transmembrane channel through which ions may pass in response to acetylcholine binding.
ACF complex An ISWI complex that contains an ATPase subunit of the ISWI family (SNF2H in mammals, Isw2 in S. cerevisiae), an ACF1 homolog, and generally no other subunits, though Xenopus is an exception with a third non-conserved subunit. ACF plays roles in regulation of RNA polymerase II transcription and in DNA replication and repair.
acrosomal membrane The membrane that surrounds the acrosomal lumen. The acrosome is a special type of lysosome in the head of a spermatozoon that contains acid hydrolases and is concerned with the breakdown of the outer membrane of the ovum during fertilization.
acrosomal vesicle A structure in the head of a spermatozoon that contains acid hydrolases, and is concerned with the breakdown of the outer membrane of the ovum during fertilization. It lies just beneath the plasma membrane and is derived from the lysosome.
actin cytoskeleton The part of the cytoskeleton (the internal framework of a cell) composed of actin and associated proteins. Includes actin cytoskeleton-associated complexes.
actin filament A filamentous structure formed of a two-stranded helical polymer of the protein actin and associated proteins. Actin filaments are a major component of the contractile apparatus of skeletal muscle and the microfilaments of the cytoskeleton of eukaryotic cells. The filaments, comprising polymerized globular actin molecules, appear as flexible structures with a diameter of 5-9 nm. They are organized into a variety of linear bundles, two-dimensional networks, and three dimensional gels. In the cytoskeleton they are most highly concentrated in the cortex of the cell just beneath the plasma membrane.
actin-based cell projection
activating signal cointegrator 1 complex
activin receptor complex A protein complex that acts as an activin receptor. Heterodimeric activin receptors, comprising one Type I activin receptor and one Type II receptor polypeptide, and heterotrimeric receptors have been observed.
activin responsive factor complex A transcriptionally active complex that binds to an activin response element (ARE) in the promoter of target genes, and is composed of two SMAD2 proteins, one SMAD4 protein and a Forkhead activin signal transducer (FAST) transcription factor.
adherens junction A cell junction at which anchoring proteins (cadherins or integrins) extend through the plasma membrane and are attached to actin filaments.
adrenomedullin receptor complex
aggresome An inclusion body formed by dynein-dependent retrograde transport of an aggregated protein on microtubules.
alpha DNA polymerase:primase complex A complex of four polypeptides, comprising large and small DNA polymerase alpha subunits and two primase subunits, which catalyzes the synthesis of an RNA primer on the lagging strand of replicating DNA; the smaller of the two primase subunits alone can catalyze oligoribonucleotide synthesis.
alpha-beta T cell receptor complex A T cell receptor complex in which the TCR heterodimer comprises alpha and beta chains, associated with the CD3 complex; recognizes a complex consisting of an antigen-derived peptide bound to a class I or class II MHC protein.
alpha9-beta1 integrin-ADAM8 complex A protein complex that consists of an alpha9-beta1 integrin complex bound to the transmembrane metallopeptidase ADAM8.
alpha9-beta1 integrin-vascular cell adhesion molecule-1 complex A protein complex that consists of an alpha9-beta1 integrin complex bound to vascular cell adhesion molecule-1.
alphav-beta3 integrin-HMGB1 complex
alphav-beta3 integrin-IGF-1-IGF1R complex A protein complex that consists of an alphav-beta3 integrin complex bound to insulin-like growth factor-1 (IGF-1) and type I insulin-like growth factor receptor (IGF1R). IGF1R is a heterotetramer that consists of two alpha-subunits and two beta-subunits.
alphav-beta3 integrin-PKCalpha complex
alphav-beta3 integrin-vitronectin complex A protein complex that consists of an alphav-beta3 integrin complex bound to vitronectin.
alveolar lamellar body A specialized secretory organelle found in type II pneumocytes and involved in the synthesis, secretion, and reutilization of pulmonary surfactant.
alveolar lamellar body membrane The lipid bilayer surrounding an alveolar lamellar body, a specialized secretory organelle found in type II pneumocytes and involved in the synthesis, secretion, and reutilization of pulmonary surfactant.
amino acid transport complex
AMPA glutamate receptor complex An assembly of four or five subunits which form a structure with an extracellular N-terminus and a large loop that together form the ligand binding domain. The C-terminus is intracellular. The ionotropic glutamate receptor complex itself acts as a ligand gated ion channel; on binding glutamate, charged ions pass through a channel in the center of the receptor complex. The AMPA receptors mediate fast synaptic transmission in the CNS and are composed of subunits GluR1-4, products from separate genes. These subunits have an extracellular N-terminus and an intracellular C-terminus.
amphisome An autophagic vacuole formed upon fusion between autophagosomes and endosomes.
amphisome membrane
amylin receptor complex
amylin receptor complex 1
amylin receptor complex 2
amylin receptor complex 3
anaphase-promoting complex A ubiquitin ligase complex that degrades mitotic cyclins and anaphase inhibitory protein, thereby triggering sister chromatid separation and exit from mitosis. Substrate recognition by APC occurs through degradation signals, the most common of which is termed the Dbox degradation motif, originally discovered in cyclin B.
AP-1 adaptor complex A heterotetrameric AP-type membrane coat adaptor complex that consists of beta1, gamma, mu1 and sigma1 subunits and links clathrin to the membrane surface of a vesicle; vesicles with AP-1-containing coats are normally found primarily in the trans-Golgi network. In at least humans, the AP-1 complex can be heterogeneric due to the existence of multiple subunit isoforms encoded by different genes (gamma1 and gamma2, mu1A and mu1B, and sigma1A, sigma1B and sigma1C).
AP-2 adaptor complex A heterotetrameric AP-type membrane coat adaptor complex that consists of alpha, beta2, mu2 and sigma2 subunits, and links clathrin to the membrane surface of a vesicle; vesicles with AP-2-containing coats are normally found primarily near the plasma membrane, on endocytic vesicles. In at least humans, the AP-2 complex can be heterogeneric due to the existence of multiple subunit isoforms encoded by different alpha genes (alphaA and alphaC).
AP-3 adaptor complex A heterotetrameric AP-type membrane coat adaptor complex that consists of beta3, delta, mu3 and sigma3 subunits and is found associated with endosomal membranes. AP-3 does not appear to associate with clathrin in all organisms. In at least humans, the AP-3 complex can be heterogeneric due to the existence of multiple subunit isoforms encoded by different genes (beta3A and beta3B, mu3A and mu3B, and sigma3A and sigma3B).
AP-4 adaptor complex An AP-type membrane coat adaptor complex that consists of beta4, epsilon, mu4 and sigma4 subunits and is found associated with membranes in the trans-Golgi network; it is not clear whether AP-4 forms clathrin coats in vivo.
AP-5 adaptor complex An AP-type membrane coat adaptor complex that in humans consists of beta5, zeta, mu5 and sigma5 subunits and is found associated with membranes in the endosomes; it is not clear whether AP-5 forms clathrin coats in vivo.
apical dendrite A dendrite that emerges near the apical pole of a neuron. In bipolar neurons, apical dendrites are located on the opposite side of the soma from the axon.
apical distal dendrite
apical junction complex A functional unit located near the cell apex at the points of contact between epithelial cells, which in vertebrates is composed of the tight junction, the zonula adherens, and desmosomes and in some invertebrates, such as Drosophila, is composed of the subapical complex (SAC), the zonula adherens and the septate junction. Functions in the regulation of cell polarity, tissue integrity and intercellular adhesion and permeability.
apicolateral plasma membrane The apical end of the lateral plasma membrane of epithelial cells.
astral microtubule Any of the spindle microtubules that radiate in all directions from the spindle poles and are thought to contribute to the forces that separate the poles and position them in relation to the rest of the cell.
astrocyte end-foot Terminal process of astrocyte abutting non-neuronal surfaces in the brain.
astrocyte projection A prolongation or process extending from the soma of an astrocyte and wrapping around neurons.
asymmetric synapse A type of synapse occurring between an axon and a dendritic spine or dendritic shaft. Asymmetric synapses, the most abundant synapse type in the central nervous system, involve axons that contain predominantly spherical vesicles and contain a thickened postsynaptic density.
asymmetric, glutamatergic, excitatory synapse
ATAC complex
ATF1-ATF4 transcription factor complex
ATF4-CREB1 transcription factor complex
ATP-binding cassette (ABC) transporter complex A complex for the transport of metabolites into and out of the cell, typically comprised of four domains; two membrane-associated domains and two ATP-binding domains at the intracellular face of the membrane, that form a central pore through the plasma membrane. Each of the four core domains may be encoded as a separate polypeptide or the domains can be fused in any one of a number of ways into multidomain polypeptides. In Bacteria and Archaebacteria, ABC transporters also include substrate binding proteins to bind substrate external to the cytoplasm and deliver it to the transporter.
ATPase dependent transmembrane transport complex A transmembrane protein complex that functions in ATPase dependent active transport across a membrane.
autolysosome A type of secondary lysosome in which a primary lysosome has fused with the outer membrane of an autophagosome. It is involved in the second step of autophagy in which it degrades contents with acidic lysosomal hydrolases.
autophagosome A double-membrane-bounded compartment in which endogenous cellular material is sequestered; known as autophagosome in yeast.
autophagosome membrane The lipid bilayer surrounding an autophagic vacuole, a double-membrane-bounded vesicle in which endogenous cellular material is sequestered.
axon The long process of a neuron that conducts nerve impulses, usually away from the cell body to the terminals and varicosities, which are sites of storage and release of neurotransmitter.
axon cytoplasm
axonal growth cone The migrating motile tip of a growing nerve cell axon.
azurophil granule Primary lysosomal granule found in neutrophil granulocytes. Contains a wide range of hydrolytic enzymes and is released into the extracellular fluid.
azurophil granule lumen The volume enclosed by the membrane of an azurophil granule, a primary lysosomal granule found in neutrophil granulocytes that contains a wide range of hydrolytic enzymes and is released into the extracellular fluid.
azurophil granule membrane The lipid bilayer surrounding an azurophil granule, a primary lysosomal granule found in neutrophil granulocytes that contains a wide range of hydrolytic enzymes and is released into the extracellular fluid.
B-WICH complex
Barr body A structure found in a female mammalian cell containing an unpaired X chromosome that has become densely heterochromatic, silenced and localized at the nuclear periphery.
basal dendrite A dendrite that emerges near the basal pole of a neuron. In bipolar neurons, basal dendrites are either on the same side of the soma as the axon, or project toward the axon.
basal ectoplasmic specialization
basement membrane A thin layer of dense material found in various animal tissues interposed between the cells and the adjacent connective tissue. It consists of the basal lamina plus an associated layer of reticulin fibers.
basolateral plasma membrane The region of the plasma membrane that includes the basal end and sides of the cell. Often used in reference to animal polarized epithelial membranes, where the basal membrane is the part attached to the extracellular matrix, or in plant cells, where the basal membrane is defined with respect to the zygotic axis.
bBAF complex
Bcl3/NF-kappaB2 complex A protein complex containing one Bcl protein and one or more copies of NF-kappaB2; formation of complexes of different stoichiometry depends on the Bcl3:NF-kappaB2 ratio, and allow Bcl3 to exert different regulatory effects on NF-kappaB2-dependent transcription.
BCOR complex
beta-catenin-TCF complex
beta-catenin-TCF7L2 complex A protein complex that contains beta-catenin and TCF7L2 (TCF4), binds to the TCF DNA motif within a promoter element, and is involved in the regulation of WNT target gene transcription.
bicellular tight junction An occluding cell-cell junction that is composed of a branching network of sealing strands that completely encircles the apical end of each cell in an epithelial sheet; the outer leaflets of the two interacting plasma membranes are seen to be tightly apposed where sealing strands are present. Each sealing strand is composed of a long row of transmembrane adhesion proteins embedded in each of the two interacting plasma membranes.
bleb A cell extension characterized by rapid formation, rounded shape, and scarcity of organelles within the protrusions.
BLOC-1 complex A protein complex required for the biogenesis of specialized organelles of the endosomal-lysosomal system, such as melanosomes and platelet dense granules. Many of the protein subunits are conserved between mouse and human; the mouse complex contains the Pallidin, Muted, Cappuccino, Dysbindin, Snapin, BLOS1, BLOS2, AND BLOS3 proteins.
BLOC-2 complex A protein complex required for the biogenesis of specialized organelles of the endosomal-lysosomal system, such as melanosomes and platelet dense granules. The human complex contains the Hps3, Hps5, and Hps6 proteins; the mouse complex contains ru2 and ru.
BLOC-3 complex A protein complex required for the biogenesis of specialized organelles of the endosomal-lysosomal system, such as melanosomes and platelet dense granules. The human complex contains the Hps1 and Hps4 proteins.
BMP receptor complex A protein complex that acts as a receptor for bone morphogenetic proteins (BMPs); a homo- or heterodimer of type I and/or type II BMP receptor subunits.
bounding membrane of organelle The lipid bilayer that forms the outer-most layer of an organelle.
box C/D RNP complex A ribonucleoprotein complex containing small nucleolar RNA of the box C/D type that can carry out ribose-2'-O-methylation of target RNAs.
brahma complex A SWI/SNF-type complex that contains the ATPase product of the Drosophila brahma gene, or an ortholog thereof.
BRCA1-BARD1 complex A heterodimeric complex comprising BRCA1 and BARD1, which possesses ubiquitin ligase activity and is involved in genome maintenance, possibly by functioning in surveillance for DNA damage.
brush border membrane The portion of the plasma membrane surrounding the brush border.
C/EBP complex
calcitonin family receptor complex
calcium channel complex An ion channel complex through which calcium ions pass.
calcium ion-transporting ATPase complex Protein complex that carries out the reaction: ATP + H2O + Ca2+(out) = ADP + phosphate + Ca2+(in).
calyx of Held The terminal specialization of a calyciferous axon which forms large synapses in the mammalian auditory central nervous system.
cardiac myofibril
caspase complex
catalase complex
catenin complex Complex of peripheral cytoplasmic proteins (alpha-, beta- and gamma-catenin) that interact with the cytoplasmic region of uvomorulin/E-cadherin to connect it to the actin cytoskeleton.
cation channel complex An ion channel complex through which cations pass.
cation-transporting ATPase complex Protein complex that carries out the reaction: ATP + H2O + cation(out) = ADP + phosphate + cation(in).
CatSper complex A sperm-specific voltage-gated calcium channel that controls the intracellular calcium ion concentration and, thereby, the swimming behavior of sperm. Consists of a heteromeric tetramer surrounding a calcium ion- selective pore. May also contain additional auxiliary subunits.
caveola A membrane raft that forms small pit, depression, or invagination that communicates with the outside of a cell and extends inward, indenting the cytoplasm and the cell membrane. Examples include any of the minute pits or incuppings of the cell membrane formed during pinocytosis. Such caveolae may be pinched off to form free vesicles within the cytoplasm.
caveola neck
CCAAT-binding factor complex A heteromeric transcription factor complex that binds to the CCAAT-box upstream of promoters; in Saccharomyces it activates the transcription of genes in response to growth in a nonfermentable carbon source; consists of four known subunits: HAP2, HAP3, HAP4 and HAP5.
CD40 receptor complex A protein complex that contains at least CD40 (a cell surface receptor of the tumour necrosis factor receptor (TNFR) superfamily), and other signaling molecules.
CD95 death-inducing signaling complex A protein complex formed upon binding of Fas/CD95/APO-1 to its ligand. The complex includes FADD/Mort1, procaspase-8/10 and c-FLIP in addition to the ligand-bound receptor.
Cdc73/Paf1 complex A multiprotein complex that associates with RNA polymerase II and general RNA polymerase II transcription factor complexes and may be involved in both transcriptional initiation and elongation. In Saccharomyces the complex contains Paf1p, Cdc73p, Ctr9p, Rtf1p, and Leo1p.
cell body fiber A neuron projection that is found in unipolar neurons and corresponds to the region between the cell body and the point at which the single projection branches.
cell cortex region
cell projection membrane The portion of the plasma membrane surrounding a cell surface projection.
cell-cell contact zone Extended zone of intimate apposition between two cells containing one or more types of intercellular junctions, e.g., the intercalated disk of muscle.
cell-cell junction A cell junction that forms a connection between two cells; excludes direct cytoplasmic junctions such as ring canals.
cell-substrate junction A cell junction that forms a connection between a cell and the extracellular matrix.
cellularization cleavage furrow
CENP-A containing chromatin
CENP-A containing nucleosome A form of nucleosome located only at the centromere, in which the histone H3 is replaced by the variant form CENP-A (sometimes known as CenH3).
cerebellar mossy fiber An axon arising from cerebellar projecting cells in the cochlea, vestibular nuclei, spinal cord, reticular formation, cerebellar nuclei and basilar pontine nuclei. Mossy fibers enter through all three cerebellar peduncles and send collaterals to the deep cerebellar nuclei, then branch in the white matter and terminate in the granule cell layer. Through this branching, a given mossy fiber can innervate several folia. Mossy fibers synapse on granule cells. The synaptic contacts are made at enlargements along the length of the mossy fiber called mossy fiber rosettes. The enlargements of the rosettes give the axons as mossy appearance in Golgi stained preparations.
CERF complex An ISWI complex that contains an ATPase subunit of the ISWI family (specifically SNF2L in mammals, which contain two ISWI homologs) and a CECR2 homolog. In mammals, CERF is involved in regulation of transcription from RNA polymerase II promoters.
CGRP receptor complex
chitosome An intracellular membrane-bounded particle found in fungi and containing chitin synthase; it synthesizes chitin microfibrils. Chitin synthase activity exists in chitosomes and they are proposed to act as a reservoir for regulated transport of chitin synthase enzymes to the division septum.
chloride channel complex An ion channel complex through which chloride ions pass.
cholinergic synapse
CHOP-ATF4 complex
CHOP-C/EBP complex A heterodimeric protein complex that is composed of the transcription factor CHOP (GADD153) and a member of the C/EBP family of transcription factors.
CHRAC An ISWI complex that contains an ATPase subunit of the ISWI family (SNF2H in mammals, Isw2 in S. cerevisiae), an ACF1 homolog, and additional small histone fold subunits (generally two of these, but Xenopus has only one and some additional non-conserved subunits). CHRAC plays roles in the regulation of RNA polymerase II transcription and in DNA replication and repair.
chromaffin granule Specialized secretory vesicle found in the cells of adrenal glands and various other organs, which is concerned with the synthesis, storage, metabolism, and secretion of epinephrine and norepinephrine.
chromaffin granule membrane The lipid bilayer surrounding a chromaffin granule, a specialized secretory vesicle found in the cells of adrenal glands and various other organs, which is concerned with the synthesis, storage, metabolism, and secretion of epinephrine and norepinephrine.
chromatin lock complex
chromatoid body A ribonucleoprotein complex found in the cytoplasm of male germ cells, composed of exceedingly thin filaments that are consolidated into a compact mass or into dense strands of varying thickness that branch to form an irregular network. Contains mRNAs, miRNAs, and protein components involved in miRNA processing (such as Argonaute proteins and the endonuclease Dicer) and in RNA decay (such as the decapping enzyme DCP1a and GW182).
chromocenter A region in which centric, heterochromatic portions of one or more chromosomes form a compact structure.
chromosome A structure composed of a very long molecule of DNA and associated proteins (e.g. histones) that carries hereditary information.
chromosome, subtelomeric region
chromosome, telomeric repeat region
chylomicron A large lipoprotein particle (diameter 75-1200 nm) composed of a central core of triglycerides and cholesterol surrounded by a protein-phospholipid coating. The proteins include one molecule of apolipoprotein B-48 and may include a variety of apolipoproteins, including APOAs, APOCs and APOE. Chylomicrons are found in blood or lymph and carry lipids from the intestines into other body tissues.
chylomicron remnant A lipoprotein particle that is derived from a mature chylomicron particle by the removal of triglycerides from the chylomicron core by lipoprotein lipase and the subsequent loss of surface components. It characteristically contains apolipoprotein E (APOE) and is cleared from the blood by the liver.
ciliary membrane The portion of the plasma membrane surrounding a cilium.
ciliary neurotrophic factor receptor complex A protein complex that acts as a receptor for the cytokine ciliary neurotrophic factor (CNTF). In humans the receptor complex is a hexamer composed of two molecules each of CNTF and CNTFR and one molecule each of gp130 and LIFR.
ciliary plasm All of the contents of a cilium, excluding the plasma membrane surrounding the cilium.
cilium A specialized eukaryotic organelle that consists of a filiform extrusion of the cell surface and of some cytoplasmic parts. Each cilium is largely bounded by an extrusion of the cytoplasmic (plasma) membrane, and contains a regular longitudinal array of microtubules, anchored to a basal body.
cis-Golgi network The network of interconnected tubular and cisternal structures located at the convex side of the Golgi apparatus, which abuts the endoplasmic reticulum.
cis-Golgi network membrane The lipid bilayer surrounding any of the compartments that make up the cis-Golgi network.
classical Lewy body Cytoplasmic inclusion, 5 to 15 micrometers in diameter, with a dense core surrounded by a halo of 10 to 20 nm wide radially oriented alpha-synuclein fibrils.
clathrin adaptor complex A membrane coat adaptor complex that links clathrin to a membrane.
clathrin coat A membrane coat found on coated pits and some coated vesicles; consists of polymerized clathrin triskelions, each comprising three clathrin heavy chains and three clathrin light chains, linked to the membrane via one of the AP adaptor complexes.
clathrin coat of coated pit The coat found on coated pits and the coated vesicles derived from coated pits; comprises clathrin and the AP-2 adaptor complex.
clathrin coat of endocytic vesicle A clathrin coat found on an endocytic vesicle.
clathrin coat of trans-Golgi network vesicle A clathrin coat found on a vesicle of the trans-Golgi network.
clathrin vesicle coat A clathrin coat found on a vesicle.
clathrin-coated endocytic vesicle A clathrin-coated, membrane-bounded intracellular vesicle formed by invagination of the plasma membrane around an extracellular substance.
clathrin-coated endocytic vesicle membrane The lipid bilayer surrounding a clathrin-coated endocytic vesicle.
clathrin-coated vesicle A vesicle with a coat formed of clathrin connected to the membrane via one of the clathrin adaptor complexes.
clathrin-coated vesicle membrane The lipid bilayer surrounding a clathrin-coated vesicle.
clathrin-sculpted acetylcholine transport vesicle A clathrin-sculpted lipid bilayer membrane-enclosed vesicle after clathrin release and containing acetylcholine.
clathrin-sculpted acetylcholine transport vesicle membrane The lipid bilayer surrounding a clathrin-sculpted acetylcholine transport vesicle.
clathrin-sculpted gamma-aminobutyric acid transport vesicle A clathrin-sculpted lipid bilayer membrane-enclosed vesicle after clathrin release and containing gamma-aminobutyric acid transport vesicle.
clathrin-sculpted gamma-aminobutyric acid transport vesicle membrane The lipid bilayer surrounding a clathrin-sculpted gamma-aminobutyric acid transport vesicle.
clathrin-sculpted glutamate transport vesicle A clathrin-sculpted lipid bilayer membrane-enclosed vesicle after clathrin release and containing glutamate.
clathrin-sculpted glutamate transport vesicle membrane The lipid bilayer surrounding a clathrin-sculpted glutamate transport vesicle.
clathrin-sculpted monoamine transport vesicle A clathrin-sculpted lipid bilayer membrane-enclosed vesicle after clathrin release and containing monoamines.
clathrin-sculpted monoamine transport vesicle membrane The lipid bilayer surrounding a clathrin-sculpted monoamine transport vesicle.
climbing fiber The axon of inferior olive neuron that projects to the cerebellar cortex, largely via the inferior cerebellar peduncle. They range in diameter from 1-3 um and are myelinated until they enter the granule cell layer. They give off collaterals to the deep cerebellar nuclei. They synapse extensively with the dendrites of Purkinje cells in the molecular layer, where each fiber branches repeatedly to climb along the Purkinje cell dendritic tree. Each Purkinje cell is innervated by only a single climbing fiber.
CLOCK-BMAL transcription complex
CMG complex A protein complex that contains the GINS complex, Cdc45p, and the heterohexameric MCM complex, and that is involved in unwinding DNA during replication.
coated vesicle Small membrane-bounded organelle formed by pinching off of a coated region of membrane. Some coats are made of clathrin, whereas others are made from other proteins.
coated vesicle membrane The lipid bilayer surrounding a coated vesicle.
collagen type I trimer A collagen trimer containing alpha(I) chains. The most common form of type I collagen is a heterotrimer containing two alpha1(I) chains and one alpha2(I) chain; homotrimers containing three alpha1(I) chains are also found. Type I collagen triple helices associate to form banded fibrils.
collagen type II trimer A collagen homotrimer of alpha1(II) chains; type II collagen triple helices associate to form fibrils.
collagen type III trimer A collagen homotrimer of alpha1(III) chains; type III collagen triple helices associate to form fibrils.
collagen type IV trimer A collagen heterotrimer containing type IV alpha chains; [alpha1(IV)]2alpha2(IV) trimers are commonly observed, although more type IV alpha chains exist and may be present in type IV trimers; type IV collagen triple helices associate to form 3 dimensional nets within basement membranes.
collagen type IX trimer A collagen heterotrimer containing type IX alpha chains in alpha1(IX)alpha2(IX)alpha3(IX) trimers; type IX collagen triple helices associate to form a structure that links glycosaminoglycans to type II collagen fibrils.
collagen type V trimer A collagen heterotrimer containing type V alpha chains; [alpha1(V)]2alpha2(V) and alpha1(V)alpha2(V)alpha3(V) trimers have been observed; type V collagen triple helices associate to form fibrils.
collagen type VII anchoring fibril
collagen type VII trimer A collagen homotrimer of alpha1(VII) chains; type VII collagen triple helices form antiparallel dimer, which in turn associate laterally to form anchoring fibrils that connect type IV collagen in the basal lamina to plaques in the underlying connective tissue. It binds laminin.
collagen type VIII trimer A collagen heterotrimer containing type VIII alpha chains; [alpha1(VIII)2]alpha2(VIII) and alpha1(VIII)[alpha2(VIII)]2 trimers have been observed; type VIII collagen triple helices associate to form regular hexagonal nets.
collagen type X trimer A collagen homotrimer of alpha1(X) chains; type X collagen triple helices form hexagonal networks (sheets).
collagen type XI trimer A collagen heterotrimer containing type XI alpha chains in alpha1(XI)alpha2(XI)alpha3(XI) trimers; type XI collagen triple helices associate to form fibrils.
collagen type XII trimer A collagen homotrimer of alpha1(XII) chains; type XII collagen triple helices may link sheet-forming or fibrillar collagens to other structures.
collagen type XIII trimer A collagen homotrimer of alpha1(XIII) chains; type XIII collagen triple helices span the plasma membrane.
collagen type XIV trimer A collagen homotrimer of alpha1(XIV) chains; type XIV collagen triple helices may link sheet-forming or fibrillar collagens to other structures.
collagen type XV trimer A collagen homotrimer of alpha1(XV) chains; a chondroitin sulfate proteoglycan often found in specialized basement membranes where it bridges between fibrils.
collagen type XVI trimer A collagen trimer containing alpha(XVI) chains; type XVI trimers can associate with microfibrils.
collagen-containing extracellular matrix
commitment complex A spliceosomal complex that is formed by association of the U1 snRNP with the 5' splice site of an unspliced intron in an RNA transcript.
condensed chromosome A highly compacted molecule of DNA and associated proteins resulting in a cytologically distinct structure.
condensed chromosome, centromeric region The region of a condensed chromosome that includes the centromere and associated proteins, including the kinetochore. In monocentric chromosomes, this region corresponds to a single area of the chromosome, whereas in holocentric chromosomes, it is evenly distributed along the chromosome.
condensed nuclear chromosome A highly compacted molecule of DNA and associated proteins resulting in a cytologically distinct structure that remains in the nucleus.
connexin complex An assembly of six molecules of connexin, made in the Golgi apparatus and subsequently transported to the plasma membrane, where docking of two connexons on apposed plasma membranes across the extracellular space forms a gap junction.
COPI vesicle coat One of two multimeric complexes that forms a membrane vesicle coat. The mammalian COPI subunits are called alpha-, beta-, beta'-, gamma-, delta-, epsilon- and zeta-COP. Vesicles with COPI coats are found associated with Golgi membranes at steady state.
COPI-coated vesicle A vesicle with a coat formed of the COPI coat complex proteins. COPI-coated vesicles are found associated with Golgi membranes at steady state, are involved in Golgi to endoplasmic reticulum (retrograde) vesicle transport, and possibly also in intra-Golgi transport.
COPI-coated vesicle membrane The lipid bilayer surrounding a COPI-coated vesicle.
COPII vesicle coat One of two multimeric complexes that forms a membrane vesicle coat. COPII is best characterized in S. cerevisiae, where the subunits are called Sar1p, Sec13p, Sec31p, Sec23p, and Sec24p. Vesicles with COPII coats are found associated with endoplasmic reticulum (ER) membranes at steady state.
COPII-coated ER to Golgi transport vesicle A vesicle that mediates transport from the endoplasmic reticulum to the Golgi complex; bears a coat formed of the COPII coat complex proteins; such vesicles found associated with endoplasmic reticulum (ER) membranes at steady state, and are involved in ER to Golgi (anterograde) vesicle transport.
core mediator complex A protein complex that interacts with the carboxy-terminal domain of the largest subunit of RNA polymerase II and plays an active role in transducing the signal from a transcription factor to the transcriptional machinery. The core mediator complex has a stimulatory effect on basal transcription, and contains most of the same subdomains as the larger form of mediator complex -- a head domain comprising proteins known in Saccharomyces as Srb2, -4, and -5, Med6, -8, and -11, and Rox3 proteins; a middle domain comprising Med1, -4, and -7, Nut1 and -2, Cse2, Rgr1, Soh1, and Srb7 proteins; and a tail consisting of Gal11p, Med2p, Pgd1p, and Sin4p -- but lacks the regulatory subcomplex comprising Ssn2, -3, and -8, and Srb8 proteins. Metazoan core mediator complexes have similar modular structures and include homologs of yeast Srb and Med proteins.
core TFIIH complex portion of holo TFIIH complex
core-binding factor complex
cornified envelope A type of plasma membrane that has been modified through addition of distinct intracellular and extracellular components, including ceramide, found in cornifying epithelial cells (corneocytes).
cortical actin cytoskeleton The portion of the actin cytoskeleton, comprising filamentous actin and associated proteins, that lies just beneath the plasma membrane.
cortical cytoskeleton The portion of the cytoskeleton that lies just beneath the plasma membrane.
cortical endoplasmic reticulum A cortical network of highly dynamic tubules that are juxtaposed to the plasma membrane and undergo ring closure and tubule-branching movements.
cortical granule A secretory vesicle that is stored under the cell membrane of an egg. These vesicles fuse with the egg plasma membrane as part of egg activation and are part of the block to polyspermy.
cortical microtubule Arrays of microtubules underlying and connected to the plasma membrane in the cortical cytosol.
cortical microtubule cytoskeleton The portion of the microtubule cytoskeleton that lies just beneath the plasma membrane.
CST complex
Cul2-RING ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul2 subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by an elongin-BC adaptor and a SOCS/BC box protein.
Cul3-RING ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul3 subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by a BTB-domain-containing protein.
Cul4-RING E3 ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul4 family and a RING domain protein form the catalytic core; substrate specificity is conferred by an adaptor protein.
Cul4A-RING E3 ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul4A subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by an adaptor protein.
Cul4B-RING E3 ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul4B subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by unknown subunits.
Cul5-RING ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul5 subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by an elongin-BC adaptor and a SOCS/BC box protein.
Cul7-RING ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul7 subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by a Skp1 linker and an F-box protein.
cullin-RING ubiquitin ligase complex Any ubiquitin ligase complex in which the catalytic core consists of a member of the cullin family and a RING domain protein; the core is associated with one or more additional proteins that confer substrate specificity.
cyclin A2-CDK2 complex A protein complex consisting of cyclin A2 and cyclin-dependent kinase 2 (CDK2). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin B1-CDK1 complex A protein complex consisting of cyclin B1 and cyclin-dependent kinase 1 (CDK1). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin D1-CDK4 complex A protein complex consisting of cyclin D1 and cyclin-dependent kinase 4 (CDK4). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin D2-CDK4 complex A protein complex consisting of cyclin D2 and cyclin-dependent kinase 4 (CDK4). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin D3-CDK4 complex A protein complex consisting of cyclin D3 and cyclin-dependent kinase 4 (CDK4). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin E1-CDK2 complex A protein complex consisting of cyclin E1 and cyclin-dependent kinase 2 (CDK2). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin E2-CDK2 complex A protein complex consisting of cyclin E2 and cyclin-dependent kinase 2 (CDK2). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin K-CDK12 complex A protein complex consisting of cyclin Kand cyclin-dependent kinase 12 (CDK12). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin K-CDK13 complex A protein complex consisting of cyclin Kand cyclin-dependent kinase 13 (CDK13). Cyclins are characterized by periodicity in protein abundance throughout the cell cycle. Cyclin-dependent kinases represent a family of serine/threonine protein kinases that become active upon binding to a cyclin regulatory partner.
cyclin-dependent protein kinase holoenzyme complex Cyclin-dependent protein kinases (CDKs) are enzyme complexes that contain a kinase catalytic subunit associated with a regulatory cyclin partner.
cyclin/CDK positive transcription elongation factor complex A transcription elongation factor complex that facilitates the transition from abortive to productive elongation by phosphorylating the CTD domain of the large subunit of DNA-directed RNA polymerase II, holoenzyme. Contains cyclin T and a cyclin-dependent protein kinase catalytic subunit.
cytolytic granule A specialized secretory lysosome that is present in cells with cytolytic capability such as cytotoxic T lymphocytes and natural killer cells. Cytolytic granules mediate the storage and regulated excretion of lytic molecules for killing of target cells.
cytolytic granule membrane
cytoophidium A subcellular filamentary structure where CTP synthase is compartmentalized in a range of organisms including bacteria, yeast, fruit fly, rat and human.
cytoplasmic dynein complex Any dynein complex that catalyzes movement along a cytoplasmic microtubule; cytoplasmic dynein complexes participates in many transport activities in eukaryotes, such as mRNA localization, intermediate filament transport, nuclear envelope breakdown, apoptosis, transport of centrosomal proteins, mitotic spindle assembly, virus transport, kinetochore functions, and movement of signaling and spindle checkpoint proteins. Subunits associated with the dynein heavy chain mediate association between dynein heavy chain and cargoes,and may include light chains and light intermediate chains.
cytoplasmic side of apical plasma membrane
cytoplasmic side of early endosome membrane The side (leaflet) of the early endosome membrane that faces the cytoplasm.
cytoplasmic side of endoplasmic reticulum membrane The side (leaflet) of the plasma membrane that faces the cytoplasm.
cytoplasmic side of endosome membrane The side (leaflet) of the endosome membrane that faces the cytoplasm.
cytoplasmic side of late endosome membrane
cytoplasmic side of lysosomal membrane
cytoplasmic side of mitochondrial outer membrane The external (cytoplasmic) face of the mitochondrial outer membrane.
cytoplasmic side of plasma membrane The leaflet the plasma membrane that faces the cytoplasm and any proteins embedded or anchored in it or attached to its surface.
cytoplasmic side of rough endoplasmic reticulum membrane
cytoplasmic side of trans-Golgi network transport vesicle membrane
cytoplasmic side of transport vesicle membrane
cytoplasmic stress granule A dense aggregation in the cytosol composed of proteins and RNAs that appear when the cell is under stress.
cytoplasmic vesicle lumen The volume enclosed by the membrane of a cytoplasmic membrane-bounded vesicle.
cytoplasmic vesicle membrane The lipid bilayer surrounding a cytoplasmic vesicle.
cytoskeleton Any of the various filamentous elements that form the internal framework of cells, and typically remain after treatment of the cells with mild detergent to remove membrane constituents and soluble components of the cytoplasm. The term embraces intermediate filaments, microfilaments, microtubules, the microtrabecular lattice, and other structures characterized by a polymeric filamentous nature and long-range order within the cell. The various elements of the cytoskeleton not only serve in the maintenance of cellular shape but also have roles in other cellular functions, including cellular movement, cell division, endocytosis, and movement of organelles.
cytoskeleton of presynaptic active zone The specialized cytoskeletal matrix assembled at the active zones of the presynaptic nerve terminal. The cytoskeletal matrix is a proteinaceous structure involved in organizing synaptic events such as immobilisation or translocation of synaptic vesicles, and assembling active zone components. The cytomatrix protein exclusively assembled at active zones, is thought to form a molecular scaffold that organizes neurotransmitter release sites.
cytosolic large ribosomal subunit The large subunit of a ribosome located in the cytosol.
cytosolic small ribosomal subunit The small subunit of a ribosome located in the cytosol.
DAPK1-calmodulin complex
death-inducing signaling complex A protein complex formed by the association of signaling proteins with a death receptor upon ligand binding. The complex includes procaspases and death domain-containing proteins in addition to the ligand-bound receptor, and may control the activation of caspases 8 and 10.
dehydrodolichyl diphosphate synthase complex
dendrite A neuron projection that has a short, tapering, often branched, morphology, receives and integrates signals from other neurons or from sensory stimuli, and conducts a nerve impulse towards the axon or the cell body. In most neurons, the impulse is conveyed from dendrites to axon via the cell body, but in some types of unipolar neuron, the impulse does not travel via the cell body.
dendrite cytoplasm All of the contents of a dendrite, excluding the surrounding plasma membrane.
dendrite membrane The portion of the plasma membrane surrounding a dendrite.
dendritic branch A dendrite arising from another dendrite.
dendritic filopodium
dendritic microtubule Any microtubule in a dendrite, a neuron projection.
dendritic spine membrane The portion of the plasma membrane surrounding a dendritic spine.
dense core granule Electron-dense organelle with a granular internal matrix; contains proteins destined to be secreted.
dense core granule lumen
dense core granule membrane The lipid bilayer surrounding a dense core granule.
dentate gyrus mossy fiber Distinctive, unmyelinated axons produced by granule cells.
desmosome A cell-cell junction in which: on the cytoplasmic surface of each interacting plasma membrane is a dense plaque composed of a mixture of intracellular anchor proteins; a bundle of keratin intermediate filaments is attached to the surface of each plaque; transmembrane adhesion proteins of the cadherin family bind to the plaques and interact through their extracellular domains to hold the adjacent membranes together by a Ca2+-dependent mechanism.
deuterosome A spherical, electron dense, cytoplasmic structure that is involved in de novo assembly of centrioles.
dihydrolipoyl dehydrogenase complex A protein complex that possesses alpha-ketoglutarate dehydrogenase activity.
dimeric IgA immunoglobulin complex A protein complex composed of two monomeric IgA immunoglobulin complexes linked through both direct disulfide bonds and through a disulfide binded monomer of J chain acting as a bridge. Each IgA monomer consists of two identical immunoglobulin heavy chains of an IgA isotype and two identical immunoglobulin light chains, held together by disulfide bonds. Dimeric IgA is sometimes complexed additionally with secretory component, and present in the extracellular space, in mucosal areas or other tissues, or circulating in the blood or lymph.
discoidal high-density lipoprotein particle A newly formed high-density lipoprotein particle; consists of a phospholipid bilayer surrounded by two or more APOA1 molecules. The discoidal HDL particle is formed when lipid-free or lipid-poor APOA1 acquires phospholipids and unesterified cholesterol from either cell membranes or triglyceride-rich lipoproteins (undergoing lipolysis by lipoprotein lipase).
distal dendrite
DNA polymerase III complex The DNA polymerase III holoenzyme is a complex that contains 10 different types of subunits. These subunits are organized into 3 functionally essential sub-assemblies: the pol III core, the beta sliding clamp processivity factor and the clamp-loading complex. The pol III core carries out the polymerase and the 3'-5' exonuclease proofreading activities. The polymerase is tethered to the template via the sliding clamp processivity factor. The clamp-loading complex assembles the beta processivity factor onto the primer template and plays a central role in the organization and communication at the replication fork.
dolichol-phosphate-mannose synthase complex A protein complex that possesses dolichyl-phosphate beta-D-mannosyltransferase activity; contains a catalytic subunit, a regulatory subunit, and a third subunit that stabilizes the complex. In human and several other metazoa, the subunits are named DPM1, DPM2 and DPM3, respectively.
dopaminergic synapse
DSIF complex A heterodimeric protein complex formed of Spt4 and Spt5 proteins which is expressed in eukaryotes from yeast to man. DSIF is an inhibitory elongation factor that promotes RNA polymerase II transcriptional pausing, but can also stimulate transcriptional elongation under certain conditions, and may play a role in RNA processing via its physical association with mRNA capping enzymes.
dystroglycan complex A protein complex that includes alpha- and beta-dystroglycan, which are alternative products of the same gene; the laminin-binding component of the dystrophin-associated glycoprotein complex, providing a link between the subsarcolemmal cytoskeleton (in muscle cells) and the extracellular matrix. Alpha-dystroglycan is an extracellular protein binding to alpha-laminin and to beta-dystroglycan; beta-dystroglycan is a transmembrane protein which binds alpha-dystroglycan and dystrophin.
early endosome A membrane-bounded organelle that receives incoming material from primary endocytic vesicles that have been generated by clathrin-dependent and clathrin-independent endocytosis; vesicles fuse with the early endosome to deliver cargo for sorting into recycling or degradation pathways.
early endosome lumen The volume enclosed by the membrane of an early endosome.
early endosome membrane The lipid bilayer surrounding an early endosome.
early phagosome A membrane-bounded intracellular vesicle as initially formed upon the ingestion of particulate material by phagocytosis.
early phagosome membrane The lipid bilayer surrounding an early phagosome.
egg coat A specialized extracellular matrix that surrounds the ovum of animals. The egg coat provides structural support and can play an essential role in oogenesis, fertilization and early development.
elastic fiber An extracellular matrix part that consists of an insoluble core of polymerized tropoelastin monomers and a surrounding mantle of microfibrils. Elastic fibers provide elasticity and recoiling to tissues and organs, and maintain structural integrity against mechanical strain.
elongin complex A transcription elongation factor complex that suppresses RNA polymerase II pausing, and may act by promoting proper alignment of the 3'-end of nascent transcripts with the polymerase catalytic site. Consists of a transcriptionally active Elongin A subunit (abut 100 kDa)and two smaller Elongin B (about 18 kDa) and Elongin C (about 15 kDa)subunits.
EMILIN complex
endocytic vesicle A membrane-bounded intracellular vesicle formed by invagination of the plasma membrane around an extracellular substance. Endocytic vesicles fuse with early endosomes to deliver the cargo for further sorting.
endocytic vesicle lumen The volume enclosed by the membrane of an endocytic vesicle.
endocytic vesicle membrane The lipid bilayer surrounding an endocytic vesicle.
endodeoxyribonuclease complex
endolysosome An transient hybrid organelle formed by fusion of a late endosome with a lysosome, and in which active degradation takes place.
endolysosome lumen The volume enclosed by the membrane of an endolysosome. An endolysosome is a transient hybrid organelle formed by fusion of a late endosome with a lysosome.
endolysosome membrane The lipid bilayer surrounding an endolysosome. An endolysosome is a transient hybrid organelle formed by fusion of a late endosome with a lysosome.
endopeptidase complex
endoplasmic reticulum lumen The volume enclosed by the membranes of the endoplasmic reticulum.
endoplasmic reticulum membrane The lipid bilayer surrounding the endoplasmic reticulum.
endoplasmic reticulum tubular network An endoplasmic reticulum part that comprises the membranes with high curvature in cross-section.
endoplasmic reticulum tubular network membrane
endoplasmic reticulum-Golgi intermediate compartment membrane The lipid bilayer surrounding any of the compartments of the endoplasmic reticulum (ER)-Golgi intermediate compartment system.
endoribonuclease complex A protein complex which is capable of endoribonuclease activity.
endosome lumen The volume enclosed by the membrane of an endosome.
endosome membrane The lipid bilayer surrounding an endosome.
endosome to plasma membrane transport vesicle
eNoSc complex
epidermal lamellar body A specialized secretory organelle found in keratinocytes and involved in the formation of an impermeable, lipid-containing membrane that serves as a water barrier and is required for correct skin barrier function.
epidermal lamellar body membrane
epididymosome
ER to Golgi transport vesicle membrane The lipid bilayer surrounding a vesicle transporting substances from the endoplasmic reticulum to the Golgi.
ERBB3:ERBB2 complex
ERCC4-ERCC1 complex A heterodimeric nucleotide-excision repair complex that has endonuclease activity specific for bubble structures characteristic of certain DNA lesions. The subunits are known as XPF/ERCC4 and ERCC1 in mammals, and Rad1p and Rad10p in S. cerevisiae.
eRF1 methyltransferase complex
ESC/E(Z) complex A multimeric protein complex that can methylate lysine-27 and lysine-9 residues of histone H3. In Drosophila the core subunits of the complex include ESC, E(Z), CAF1 (NURF-55) and SU(Z)12. In mammals the core subunits of the complex include EED, EZH2, SUZ12 and RBBP4.
euchromatin A dispersed and relatively uncompacted form of chromatin.
eukaryotic 43S preinitiation complex A protein complex composed of the 40S ribosomal subunit plus eIF1A, eIF3, and eIF2-GTP-bound methionyl-initiator methionine tRNA.
eukaryotic 48S preinitiation complex A protein complex composed of the small ribosomal subunit, eIF3, eIF1A, methionyl-initiatior methionine and a capped mRNA. The complex is initially positioned at the 5'-end of the capped mRNA.
excitatory synapse A synapse in which an action potential in the presynaptic cell increases the probability of an action potential occurring in the postsynaptic cell.
exocytic vesicle A transport vesicle that mediates transport from an intracellular compartment to the plasma membrane, and fuses with the plasma membrane to release various cargo molecules, such as proteins or hormones, by exocytosis.
exocytic vesicle membrane
external side of apical plasma membrane
extracellular membrane-bounded organelle Organized structure of distinctive morphology and function, bounded by a lipid bilayer membrane and occurring outside the cell.
extracellular vesicle Any vesicle that is part of the extracellular region.
extrinsic component of cytoplasmic side of plasma membrane The component of a plasma membrane consisting of gene products and protein complexes that are loosely bound to its cytoplasmic surface, but not integrated into the hydrophobic region.
extrinsic component of dense core granule membrane
extrinsic component of endoplasmic reticulum membrane The component of the endoplasmic reticulum membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.
extrinsic component of endosome membrane The component of an endosome membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.
extrinsic component of external side of plasma membrane The component of a plasma membrane consisting of gene products and protein complexes that are loosely bound to its external surface, but not integrated into the hydrophobic region.
extrinsic component of Golgi membrane The component of a Golgi membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.
extrinsic component of mitochondrial inner membrane The component of mitochondrial inner membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.
extrinsic component of mitochondrial outer membrane The component of a mitochondrial outer membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.
extrinsic component of neuronal dense core vesicle membrane
extrinsic component of omegasome membrane The component of the omegasome membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.
extrinsic component of phagophore assembly site membrane The component of the pre-autophagosomal structure membrane consisting of gene products and protein complexes that are loosely bound to one of its surfaces, but not integrated into the hydrophobic region.
extrinsic component of postsynaptic early endosome membrane
extrinsic component of postsynaptic endosome membrane
extrinsic component of postsynaptic membrane
extrinsic component of presynaptic endocytic zone membrane
extrinsic component of presynaptic membrane
extrinsic component of synaptic membrane
extrinsic component of synaptic vesicle membrane
FACT complex An abundant nuclear complex, which was originally identified in mammalian systems as a factor required for transcription elongation on chromatin templates. The FACT complex has been shown to destablilize the interaction between the H2A/H2B dimer and the H3/H4 tetramer of the nucleosome, thus reorganizing the structure of the nucleosome. In this way, the FACT complex may play a role in DNA replication and other processes that traverse the chromatin, as well as in transcription elongation. FACT is composed of two proteins that are evolutionarily conserved in all eukaryotes and homologous to mammalian Spt16 and SSRP1. In metazoans, the SSRP1 homolog contains an HMG domain; however in fungi and protists, it does not. For example, in S. cerevisiae the Pob3 protein is homologous to SSRP1, but lacks the HMG chromatin binding domain. Instead, the yFACT complex of Spt16p and Pob3p, binds to nucleosomes where multiple copies of the HMG-domain containing protein Nhp6p have already bound, but Nhp6p does not form a stable complex with the Spt16p/Pob3p heterodimer.
fascia adherens A cell-cell adherens junction that contains the transmembrane protein N-cadherin, which interacts with identical molecules from neighboring cells to form a tight mechanical intercellular link; forms a large portion of the intercalated disc, the structure at which myofibrils terminate in cardiomyocytes.
Fc receptor complex A protein complex composed of a subunit or subunits capable of binding the Fc portion of an immunoglobulin with additional signaling components. The complex functions as a receptor for immunoglobulin.
Fc-epsilon receptor I complex A protein complex composed of an Fc-epsilon RI alpha chain and an Fc-epsilon RI gamma chain dimer with or without an Fc-episilon RI beta chain and additional signaling components. The complex functions primarily as an activating receptor for IgE.
Fc-gamma receptor III complex
female germ cell nucleus The nucleus of the female germ cell, a reproductive cell in females.
female pronucleus The pronucleus originating from the ovum that is being fertilized.
ficolin-1-rich granule
ficolin-1-rich granule lumen
ficolin-1-rich granule membrane
filopodium Thin, stiff protrusion extended by the leading edge of a motile cell such as a crawling fibroblast or amoeba, or an axonal or dendritic growth cone, or a dendritic shaft.
filopodium membrane The portion of the plasma membrane surrounding a filopodium.
filtration diaphragm A specialized cell-cell junction found between the cells of the excretory system, which provides a barrier for filtration of blood or hemolymph.
flotillin complex A protein complex that contains flotillin-1 and flotillin-2, and may contain associated proteins. Flotillins associate into membrane microdomains resembling caveolae.
focal adhesion Small region on the surface of a cell that anchors the cell to the extracellular matrix and that forms a point of termination of actin filaments.
G protein-coupled GABA receptor complex
G protein-coupled receptor complex A protein complex that contains G-protein coupled receptors.
G protein-coupled receptor dimeric complex A protein complex that contains two G-protein coupled receptors.
G protein-coupled receptor heterodimeric complex A protein complex that contains two G-protein coupled receptors (GPCRs) of different subtypes. Formation of a GPCR heterodimer may alter the functional property of the GPCR.
G protein-coupled receptor homodimeric complex A protein complex that contains two G-protein coupled receptors (GPCRs) of the same subtype. Formation of a GPCR homodimer may be important for the transport of newly formed receptors to the cell surface, and the function of the receptor.
G protein-coupled serotonin receptor complex
GABA-A receptor complex A protein complex which is capable of GABA-A receptor activity. In human, it is usually composed of either two alpha, two beta and one gamma chain of the GABA-A receptor subunits or 5 chains of the GABA-A receptor subunits rho1-3 (formally known as GABA-C receptor).
GABA-ergic synapse
galectin complex
gamma-catenin-TCF7L2 complex A protein complex that contains gamma-catenin and TCF7L2 (TCF4), binds to the TCF DNA motif within a promoter element, and is involved in the regulation of WNT target gene transcription.
gamma-delta T cell receptor complex A T cell receptor complex in which the TCR heterodimer comprises gamma and delta chains, associated with the CD3 complex; recognizes antigen directly, without a requirement for processing and presentation by an MHC protein.
gap junction A cell-cell junction that is composed of an array of small channels that permit small molecules to pass from one cell to another. At gap junctions, the membranes of two adjacent cells are separated by a uniform narrow gap of about 2-4 nm that is spanned by channel-forming proteins called connexins, which form hexagonal tubes called connexons.
GBAF complex
germ cell nucleus The nucleus of a germ cell, a reproductive cell in multicellular organisms.
germ plasm Differentiated cytoplasm associated with a pole of an oocyte, egg or early embryo that will be inherited by the cells that will give rise to the germ line.
germinal vesicle The enlarged, fluid filled nucleus of a primary oocyte, the development of which is suspended in prophase I of the first meiotic division between embryohood and sexual maturity.
GID complex A protein complex with ubiquitin ligase activity that is involved in proteasomal degradation of fructose-1,6-bisphosphatase (FBPase) and phosphoenolpyruvate carboxykinase during the transition from gluconeogenic to glycolytic growth conditions. In S. cerevisiae, the GID (Glucose Induced degradation Deficient) complex consists of Vid30p, Rmd5p, Vid24p, Vid28p, Gid7p, Gid8p, and Fyv10p.
GINS complex A heterotetrameric protein complex that associates with replication origins, where it is required for the initiation of DNA replication, and with replication forks.
glial cell projection A prolongation or process extending from a glial cell.
glial cytoplasmic inclusion Non-membrane-bound cytoplasmic inclusions composed of 10-40 nm granule-coated fibrils. These inclusions have an abnormal accumulation of alpha-synuclein protein and are found in association with multiple system atrophy.
glial limiting end-foot Terminal process of astrocyte that extends to the surface of the central nervous system. Together, glial limiting end-feet form the glial limiting membrane or glia limitans.
glomerular endothelium fenestra A large plasma membrane-lined circular pore that perforates the flattened glomerular endothelium and, unlike those of other fenestrated capillaries, is not spanned by diaphragms; the density and size of glomerular fenestrae account, at least in part, for the high permeability of the glomerular capillary wall to water and small solutes.
glutamatergic synapse
glycine-gated chloride channel complex A protein complex that forms a transmembrane channel through which chloride ions may pass in response to glycine binding to the channel complex or one of its constituent parts.
Golgi cis cisterna The Golgi cisterna closest to the endoplasmic reticulum; the first processing compartment through which proteins pass after export from the ER.
Golgi cis cisterna membrane
Golgi cisterna Any of the thin, flattened membrane-bounded compartments that form the central portion of the Golgi complex.
Golgi cisterna membrane The lipid bilayer surrounding any of the thin, flattened compartments that form the central portion of the Golgi complex.
Golgi lumen The volume enclosed by the membranes of any cisterna or subcompartment of the Golgi apparatus, including the cis- and trans-Golgi networks.
Golgi medial cisterna The middle Golgi cisterna (or cisternae).
Golgi medial cisterna membrane
Golgi membrane The lipid bilayer surrounding any of the compartments of the Golgi apparatus.
Golgi stack The set of thin, flattened membrane-bounded compartments, called cisternae, that form the central portion of the Golgi complex. The stack usually comprises cis, medial, and trans cisternae; the cis- and trans-Golgi networks are not considered part of the stack.
Golgi to plasma membrane transport vesicle
Golgi trans cisterna The Golgi cisterna farthest from the endoplasmic reticulum; the final processing compartment through which proteins pass before exiting the Golgi apparatus; the compartment in which N-linked protein glycosylation is completed.
Golgi trans cisterna membrane
Golgi-associated vesicle Any vesicle associated with the Golgi complex and involved in mediating transport within the Golgi or between the Golgi and other parts of the cell.
Golgi-associated vesicle lumen
Golgi-associated vesicle membrane The lipid bilayer surrounding a vesicle associated with the Golgi apparatus.
granular vesicle A cytoplasmic membrane-bounded vesicle of varying size, but usually larger than 45 nm, with an electron dense granular core, found in noradrenergic and peptidergic cells.
granulocyte macrophage colony-stimulating factor receptor complex The heterodimeric receptor for granulocyte macrophage colony-stimulating factor.
Grb2-EGFR complex A protein complex that contains the epidermal growth factor receptor (EGFR) and Grb2, and is involved in linking EGFR activation to the p21-Ras pathway.
growth cone filopodium
Gtr1-Gtr2 GTPase complex A heterodimer GTPase complex. In S. cerevisiae, this complex contains Gtr1p and Gtr2p proteins.
H3 histone acetyltransferase complex A multisubunit complex that catalyzes the acetylation of histone H3.
H4 histone acetyltransferase complex A protein complex which is capable of H4 histone acetyltransferase activity.
H4/H2A histone acetyltransferase complex A multisubunit complex that catalyzes the acetylation of histones H4 and H2A.
HCN channel complex
hemidesmosome A cell-substrate junction that forms a point of contact between the basal surface of epithelial cells and the basal lamina. Morphologically resembles desmosomes; attached to intermediate filaments.
heterochromatin A compact and highly condensed form of chromatin.
heterotrimeric G-protein complex Any of a family of heterotrimeric GTP-binding and hydrolyzing proteins; they belong to a superfamily of GTPases that includes monomeric proteins such as EF-Tu and RAS. Heterotrimeric G-proteins consist of three subunits; the alpha subunit contains the guanine nucleotide binding site and possesses GTPase activity; the beta and gamma subunits are tightly associated and function as a beta-gamma heterodimer; extrinsic plasma membrane proteins (cytoplasmic face) that function as a complex to transduce signals from G-protein coupled receptors to an effector protein.
hexameric IgM immunoglobulin complex A circulating form of IgM consisting of a hexamer of IgM core units with a single J chain polypeptide.
HFE-transferrin receptor complex
high-density lipoprotein particle A lipoprotein particle with a high density (typically 1.063-1.21 g/ml) and a diameter of 5-10 nm that contains APOAs and may contain APOCs and APOE; found in blood and carries lipids from body tissues to the liver as part of the reverse cholesterol transport process.
hippocampal mossy fiber
hippocampal mossy fiber to CA3 synapse
histone acetyltransferase complex A protein complex that possesses histone acetyltransferase activity.
Holliday junction resolvase complex A protein complex that mediates the conversion of a Holliday junction into two separate duplex DNA molecules; the complex includes a single- or multisubunit helicase that catalyzes the extension of heteroduplex DNA by branch migration and a nuclease that resolves the junction by nucleolytic cleavage.
Hrd1p ubiquitin ligase complex A multiprotein complex that recognizes and ubiquitinates proteins with misfolded luminal and membrane domains during ER-associated protein degradation (ERAD). In S. cerevisiae, this complex contains the ubiquitin ligase Hrd1p.
Hrd1p ubiquitin ligase ERAD-L complex
HULC complex A ubiquitin-conjugating enzyme complex that contains two RING finger proteins, which have ubiquitin ligase activity, in addition to a protein with ubiquitin-conjugating enzyme activity; catalyzes the ubiquitination of histone H2B at lysine 119 (or the equivalent residue). In Schizosaccharomyces the subunits are Rhp1, Brl2/Rfp1 and Brl1/Rfp2.
IgA immunoglobulin complex, circulating A protein complex composed of two identical immunoglobulin heavy chains of an IgA isotype and two identical immunoglobulin light chains, held together by disulfide bonds, sometimes complexed with J chain or J chain and secretory component, and present in the extracellular space, in mucosal areas or other tissues, or circulating in the blood or lymph.
IgM immunoglobulin complex, circulating A polymer of five or six IgM core units each composed of two identical immunoglobulin heavy chains of the IgM isotype and two identical immunoglobulin light chains, held together by disulfide bonds; the individual IgM core units are held together via disulfide bonds with a single J chain polypeptide acting as a bridge between two of the polymeric units. Circulating IgM is present in the extracellular space, in mucosal areas or other tissues, or in the blood or lymph.
inactive sex chromosome
inhibin-betaglycan-ActRII complex A protein complex that consists of inhibin, type III transforming growth factor beta receptor (also known as betaglycan), and the type II activin receptor ActRII. The complex is thought to negatively regulate the activity of activin B.
inhibitory synapse A synapse in which an action potential in the presynaptic cell reduces the probability of an action potential occurring in the postsynaptic cell.
inner acrosomal membrane The acrosomal membrane region that underlies the acrosomal vesicle and is located toward the sperm nucleus. This region is responsible for molecular interactions allowing the sperm to penetrate the zona pellucida and fuses with the egg plasma membrane.
inner dynein arm Inner arm structure present on the outer doublet microtubules of ciliary and flagellar axonemes. The structure of inner dynein arms is complex and may vary within the axoneme. Inner and outer dynein arms have different functions in the generation of microtubule-based motility.
Ino80 complex A multisubunit protein complex that contains the Ino80p ATPase; exhibits chromatin remodeling activity and 3' to 5' DNA helicase activity.
INO80-type complex A chromatin remodeling protein complex initially purified from S. cerevisiae and containing more than 10 subunits, including the SWR1-related complexes. INO80 (inositol requiring 80)-type complexes have diverse functions, including promoting transcriptional activation and DNA repair.
insulin receptor complex A disulfide-bonded, heterotetrameric receptor complex. The alpha chains are entirely extracellular, while each beta chain has one transmembrane domain. The ligand binds to the alpha subunit extracellular domain and the kinase is associated with the beta subunit intracellular domain.
insulin-like growth factor binary complex A complex of two proteins, which in animals is 50kDa and consists of the insulin-like growth factor (IGF) and one of the insulin-like growth factor binding protein-1 (IGFBP-1), -2 (IGFBP-2), -4 (IGFBP-4) and -6 (IGFBP-6). The complex plays a role in growth and development.
insulin-like growth factor ternary complex A complex of three proteins, which in animals is approximately 150kDa and consists of the insulin-like growth factor (IGF), the insulin-like growth factor binding protein-3 (IGFBP-3), or -5 (IGFBP-5) and an acid-labile subunit (ALS). The complex plays a role in growth and development.
insulin-responsive compartment A small membrane-bounded vesicle that releases its contents by exocytosis in response to insulin stimulation; the contents are enriched in GLUT4, IRAP and VAMP2.
integrin alpha1-beta1 complex An integrin complex that comprises one alpha1 subunit and one beta1 subunit.
integrin alpha10-beta1 complex An integrin complex that comprises one alpha10 subunit and one beta1 subunit.
integrin alpha11-beta1 complex An integrin complex that comprises one alpha11 subunit and one beta1 subunit.
integrin alpha2-beta1 complex An integrin complex that comprises one alpha2 subunit and one beta1 subunit.
integrin alpha3-beta1 complex An integrin complex that comprises one alpha3 subunit and one beta1 subunit.
integrin alpha4-beta1 complex An integrin complex that comprises one alpha4 subunit and one beta1 subunit.
integrin alpha4-beta7 complex An integrin complex that comprises one alpha4 subunit and one beta7 subunit.
integrin alpha5-beta1 complex An integrin complex that comprises one alpha5 subunit and one beta1 subunit.
integrin alpha8-beta1 complex An integrin complex that comprises one alpha8 subunit and one beta1 subunit.
integrin alphaL-beta2 complex An integrin complex that comprises one alphaL subunit and one beta2 subunit.
integrin alphaM-beta2 complex An integrin complex that comprises one alphaM subunit and one beta2 subunit.
integrin alphav-beta3 complex An integrin complex that comprises one alphav subunit and one beta3 subunit.
integrin alphav-beta5 complex An integrin complex that comprises one alphav subunit and one beta5 subunit.
integrin alphav-beta6 complex An integrin complex that comprises one alphav subunit and one beta6 subunit.
integrin alphav-beta8 complex An integrin complex that comprises one alphav subunit and one beta8 subunit.
integrin alphaX-beta2 complex An integrin complex that comprises one alphaX subunit and one beta2 subunit.
intercalated disc A complex cell-cell junction at which myofibrils terminate in cardiomyocytes; mediates mechanical and electrochemical integration between individual cardiomyocytes. The intercalated disc contains regions of tight mechanical attachment (fasciae adherentes and desmosomes) and electrical coupling (gap junctions) between adjacent cells.
intercellular canaliculus An extremely narrow tubular channel located between adjacent cells. An instance of this is the secretory canaliculi occurring between adjacent parietal cells in the gastric mucosa of vertebrates.
interleukin-12 receptor complex A protein complex that binds interleukin-12; comprises a beta1 and a beta2 subunit.
interleukin-13 receptor complex A protein complex that binds interleukin-13; consists of two chains, interleukin-13 receptor alpha1 chain and interleukin-4 receptor alpha chain.
interleukin-18 receptor complex A protein complex that binds interleukin-18; comprises an alpha and a beta subunit.
interleukin-2 receptor complex A protein complex that binds interleukin-2; comprises alpha, beta, and gamma subunits.
interleukin-23 receptor complex A protein complex that binds interleukin-23. The complex comprises two subunits, including the same beta subunit found in the interleukin-12 receptor.
interleukin-28 receptor complex A protein complex that binds interleukin-28 and interleukin-29. Composed of two subunits, IL-28R alpha and IL-10R beta.
interleukin-5 receptor complex A protein complex that binds interleukin-3; comprises an alpha and a beta subunit. The alpha chain is specific to the interleukin-5 receptor, whereas the beta chain is shared with the receptors for granulocyte-macrophage colony-stimulating factor and interleukin-3.
interleukin-6 receptor complex A hexameric protein complex consisting of two molecules each of interleukin-6, interleukin-6 receptor alpha chain, and gp-130.
intermediate filament A cytoskeletal structure that forms a distinct elongated structure, characteristically 10 nm in diameter, that occurs in the cytoplasm of eukaryotic cells. Intermediate filaments form a fibrous system, composed of chemically heterogeneous subunits and involved in mechanically integrating the various components of the cytoplasmic space. Intermediate filaments may be divided into five chemically distinct classes: Type I, acidic keratins; Type II, basic keratins; Type III, including desmin, vimentin and others; Type IV, neurofilaments and related filaments; and Type V, lamins.
intermediate filament cytoskeleton Cytoskeletal structure made from intermediate filaments, typically organized in the cytosol as an extended system that stretches from the nuclear envelope to the plasma membrane. Some intermediate filaments run parallel to the cell surface, while others traverse the cytosol; together they form an internal framework that helps support the shape and resilience of the cell.
intermediate-density lipoprotein particle A triglyceride-rich lipoprotein particle that typically contains APOB100, APOE and APOCs and has a density of 1.006-1.019 g/ml and a diameter of between 25-30 nm. IDL particles are found in blood and are formed by the delipidation of very-low-density lipoprotein particles (VLDL). IDL particles are removed from blood by the liver, following binding to the APOE receptor, or are converted to low-density lipoprotein (LDL).
interstitial matrix A type of extracellular matrix found in interstitial connective tissue, characterized by the presence of fibronectins, proteoglycans, and types I, III, V, VI, VII and XII collagens.
intracellular cyclic nucleotide activated cation channel complex A protein complex that forms a transmembrane channel through which cations ions may pass in response to an intracellular cyclic nucleotide binding to the channel complex or one of its constituent parts.
intracellular membrane-bounded organelle Organized structure of distinctive morphology and function, bounded by a single or double lipid bilayer membrane and occurring within the cell. Includes the nucleus, mitochondria, plastids, vacuoles, and vesicles. Excludes the plasma membrane.
intracellular non-membrane-bounded organelle Organized structure of distinctive morphology and function, not bounded by a lipid bilayer membrane and occurring within the cell. Includes ribosomes, the cytoskeleton and chromosomes.
intracellular organelle lumen An organelle lumen that is part of an intracellular organelle.
intracellular vesicle
inward rectifier potassium channel complex A protein complex which is capable of inward rectifier potassium channel activity.
inward rectifying potassium channel A protein complex that comprises four pore-forming (Kir6.x) and four regulatory sulphonylurea receptor (SURx) subunits and forms a transmembrane channel through which ions may pass. The opening and closing of the channel is regulated by ATP: binding of ATP to the Kir6.2 subunit inhibits channel activity, whereas binding of Mg2+-complexed ATP or ADP to the SUR1 subunit stimulates channel activity.
ionotropic glutamate receptor complex A multimeric assembly of four or five subunits which form a structure with an extracellular N-terminus and a large loop that together form the ligand binding domain. The C-terminus is intracellular. The ionotropic glutamate receptor complex itself acts as a ligand-gated ion channel; on binding glutamate, charged ions pass through a channel in the center of the receptor complex.
ISGF3 complex
isocitrate dehydrogenase complex (NAD+)
ISWI-type complex Any nuclear protein complex that contains an ATPase subunit of the imitation switch (ISWI) family. ISWI ATPases are involved in assembling chromatin and in sliding and spacing nucleosomes to regulate transcription of nuclear RNA polymerases I, II, and III and also DNA replication, recombination and repair.
junctional sarcoplasmic reticulum membrane The part of the sarcoplasmic reticulum membrane that contains calcium release channels, is devoted to calcium release and is juxtaposed to transverse tubule membrane. The junctional sarcoplasmic reticulum membrane consists of the junctional region of the terminal cisterna membrane.
kainate selective glutamate receptor complex An assembly of four or five subunits which form a structure with an extracellular N-terminus and a large loop that together form the ligand binding domain. The C-terminus is intracellular. The ionotropic glutamate receptor complex itself acts as a ligand gated ion channel; on binding glutamate, charged ions pass through a channel in the center of the receptor complex. Kainate receptors are multimeric assemblies of GluR5-7 and KA-1/2 subunits.
keratin filament A filament composed of acidic and basic keratins (types I and II), typically expressed in epithelial cells. The keratins are the most diverse classes of IF proteins, with a large number of keratin isoforms being expressed. Each type of epithelium always expresses a characteristic combination of type I and type II keratins.
kinesin I complex A complex of two kinesin heavy chains and two kinesin light chains.
kinesin II complex A complex consisting of two distinct motor subunits that form a heterodimer complexed with a third non-motor accessory subunit, the kinesin associated protein or KAP; the KIF3 heterodimer interacts via its C-terminal portion with KAP, which is thought to regulate the binding of the motor to cargo membranes.
kinetochore microtubule Any of the spindle microtubules that attach to the kinetochores of chromosomes by their plus ends, and maneuver the chromosomes during mitotic or meiotic chromosome segregation.
kinociliary basal body
lamellar body A membrane-bounded organelle, specialized for the storage and secretion of various substances (surfactant phospholipids, glycoproteins and acid phosphates) which are arranged in the form of tightly packed, concentric, membrane sheets or lamellae. Has some similar properties to, but is distinct from, a lysosome.
lamellar body membrane The lipid bilayer surrounding a lamellar body. A lamellar body is a membrane-bounded organelle, specialized for the storage and secretion of various substances (surfactant phospholipids, glycoproteins and acid phosphates) which are arranged in the form of tightly packed, concentric, membrane sheets or lamellae. Has some similar properties to, but is distinct from, a lysosome.
large ribosomal subunit The larger of the two subunits of a ribosome. Two sites on the ribosomal large subunit are involved in translation, namely the aminoacyl site (A site) and peptidyl site (P site).
late endosome A prelysosomal endocytic organelle differentiated from early endosomes by lower lumenal pH and different protein composition. Late endosomes are more spherical than early endosomes and are mostly juxtanuclear, being concentrated near the microtubule organizing center.
late endosome lumen The volume enclosed by the membrane of a late endosome.
late endosome membrane The lipid bilayer surrounding a late endosome.
Lewy body Cytoplasmic, spherical inclusion commonly found in damaged neurons, and composed of abnormally phosphorylated, neurofilament proteins aggregated with ubiquitin and alpha-synuclein.
Lewy neurite Elongated neuronal process, often with side branches and more than one branching point, described in brains of patients with Parkinson's disease. Lewy neurites stain positively for ubiquitin in brainstem and forebrain regions affected in Parkinson's disease.
lipid droplet An intracellular non-membrane-bounded organelle comprising a matrix of coalesced lipids surrounded by a phospholipid monolayer. May include associated proteins.
low-density lipoprotein particle A lipoprotein particle, rich in cholesterol esters and low in triglycerides that is typically composed of APOB100 and APOE and has a density of 1.02-1.06 g/ml and a diameter of between 20-25 nm. LDL particles are formed from VLDL particles (via IDL) by the loss of triglyceride and gain of cholesterol ester. They transport endogenous cholesterol (and to some extent triglycerides) from peripheral tissues back to the liver.
LUBAC complex A ubiquitin ligase complex that catalyzes linear head-to-tail polyubiquitin conjugation on its targets. In human the complex consists of RBCK1, RNF31 and SHARPIN, and has an MW of approximately 600 kDa, suggesting a heteromultimeric assembly of its subunits. LUBAC stands for Linear Ubiquitin Chain Assembly Complex.
lumenal side of endoplasmic reticulum membrane
lumenal side of lysosomal membrane
lysosomal HOPS complex
lysosomal lumen The volume enclosed within the lysosomal membrane.
lysosomal membrane The lipid bilayer surrounding the lysosome and separating its contents from the cell cytoplasm.
lysosome A small lytic vacuole that has cell cycle-independent morphology and is found in most animal cells and that contains a variety of hydrolases, most of which have their maximal activities in the pH range 5-6. The contained enzymes display latency if properly isolated. About 40 different lysosomal hydrolases are known and lysosomes have a great variety of morphologies and functions.
lytic vacuole A vacuole that is maintained at an acidic pH and which contains degradative enzymes, including a wide variety of acid hydrolases.
lytic vacuole membrane
m-AAA complex Protease complex of the mitochondrial inner membrane that is involved in mitochondrial protein turnover and in processing of proteins imported into mitochondria.
macropinocytic cup A cell projection that forms at the site of macropinocytosis, a form of endocytosis that results in the uptake of relatively large amounts of extracellular fluid. The macropinocytic cup membrane selectively excludes certain proteins, such as H36 or PM4C4 in Dictyostelium, and the underlying cytoskeleton is enriched in F-actin and coronin.
macropinosome A membrane-bounded, uncoated intracellular vesicle formed by the process of macropinocytosis.
Mad-Max complex A transcriptional repressor complex that consists of a heterodimer of the bHLH-ZIP proteins Mad and Max.
male germ cell nucleus The nucleus of a male germ cell, a reproductive cell in males.
male pronucleus The pronucleus originating from the spermatozoa that was involved in fertilization.
mast cell granule Coarse, bluish-black staining cytoplasmic granules, bounded by a plasma membrane and found in mast cells and basophils. Contents include histamine, heparin, chondroitin sulfates, chymase and tryptase.
matrix side of mitochondrial inner membrane
mature chylomicron A chylomicron that contains apolipoprotein C2 (APOC2), a cofactor for lipoprotein lipase (LPL) activity, and has a mean diameter of 500 nm and density of 0.95g/ml. Mature chylomicron particles transport exogenous (dietary) lipids from the intestines to other body tissues, via the blood and lymph.
megasporocyte nucleus The nucleus of a megasporocyte, a diploid cell that undergoes meiosis to produce four megaspores, and its descendents.
meiotic spindle A spindle that forms as part of meiosis. Several proteins, such as budding yeast Spo21p, fission yeast Spo2 and Spo13, and C. elegans mei-1, localize specifically to the meiotic spindle and are absent from the mitotic spindle.
melanosome A tissue-specific, membrane-bounded cytoplasmic organelle within which melanin pigments are synthesized and stored. Melanosomes are synthesized in melanocyte cells.
melanosome membrane The lipid bilayer surrounding a melanosome.
membrane attack complex A protein complex produced by sequentially activated components of the complement cascade inserted into a target cell membrane and forming a pore leading to cell lysis via ion and water flow.
membrane raft Any of the small (10-200 nm), heterogeneous, highly dynamic, sterol- and sphingolipid-enriched membrane domains that compartmentalize cellular processes. Small rafts can sometimes be stabilized to form larger platforms through protein-protein and protein-lipid interactions.
MHC class I protein complex A transmembrane protein complex composed of a MHC class I alpha chain and an invariant beta2-microglobin chain, and with or without a bound peptide antigen. Class I here refers to classical class I molecules.
MHC class Ib protein complex A transmembrane protein complex composed of a MHC class Ib alpha chain and, in most cases, an invariant beta2-microglobin chain, and with or without a bound peptide or lipid antigen. Class Ib here refers to non-classical class I molecules, such as those of the CD1 or HLA-E gene families.
MHC class II protein complex A transmembrane protein complex composed of an MHC class II alpha and MHC class II beta chain, and with or without a bound peptide or polysaccharide antigen.
MHC protein complex A transmembrane protein complex composed of an MHC alpha chain and, in most cases, either an MHC class II beta chain or an invariant beta2-microglobin chain, and with or without a bound peptide, lipid, or polysaccharide antigen.
MIB complex
MICOS complex
microbody lumen The volume enclosed by the membranes of a microbody.
microbody membrane The lipid bilayer surrounding a microbody.
microfibril Extracellular matrix components occurring independently or along with elastin. Thought to have force-bearing functions in tendon. In addition to fibrillins, microfibrils may contain other associated proteins.
microspike A dynamic, actin-rich projection extending from the surface of a migrating animal cell.
microtubule Any of the long, generally straight, hollow tubes of internal diameter 12-15 nm and external diameter 24 nm found in a wide variety of eukaryotic cells; each consists (usually) of 13 protofilaments of polymeric tubulin, staggered in such a manner that the tubulin monomers are arranged in a helical pattern on the microtubular surface, and with the alpha/beta axes of the tubulin subunits parallel to the long axis of the tubule; exist in equilibrium with pool of tubulin monomers and can be rapidly assembled or disassembled in response to physiological stimuli; concerned with force generation, e.g. in the spindle.
microtubule cytoskeleton The part of the cytoskeleton (the internal framework of a cell) composed of microtubules and associated proteins.
microvesicle
microvillus Thin cylindrical membrane-covered projections on the surface of an animal cell containing a core bundle of actin filaments. Present in especially large numbers on the absorptive surface of intestinal cells.
microvillus membrane The portion of the plasma membrane surrounding a microvillus.
mitochondrial alpha-ketoglutarate dehydrogenase complex Mitochondrial complex that possesses alpha-ketoglutarate dehydrogenase activity.
mitochondrial ATP-gated potassium channel complex
mitochondrial envelope The double lipid bilayer enclosing the mitochondrion and separating its contents from the cell cytoplasm; includes the intermembrane space.
mitochondrial inner membrane The inner, i.e. lumen-facing, lipid bilayer of the mitochondrial envelope. It is highly folded to form cristae.
mitochondrial intermembrane space The region between the inner and outer lipid bilayers of the mitochondrial envelope.
mitochondrial isocitrate dehydrogenase complex (NAD+)
mitochondrial matrix The gel-like material, with considerable fine structure, that lies in the matrix space, or lumen, of a mitochondrion. It contains the enzymes of the tricarboxylic acid cycle and, in some organisms, the enzymes concerned with fatty acid oxidation.
mitochondrial membrane Either of the lipid bilayers that surround the mitochondrion and form the mitochondrial envelope.
mitochondrial outer membrane The outer, i.e. cytoplasm-facing, lipid bilayer of the mitochondrial envelope.
mitochondrial outer membrane translocase complex A large complex of the mitochondrial outer membrane that mediates transport of proteins into all mitochondrial compartments.
mitochondrial oxoglutarate dehydrogenase complex
mitochondrial prohibitin complex A complex composed of two proteins, prohibitin 1 and prohibitin 2 (PHB1/PHB-1 and PHB2/PHB-2) that is highly conserved amongst eukaryotes and associated with the inner mitochondrial membrane. The mitochondrial prohibitin complex is a macromolecular supercomplex composed of repeating heterodimeric subunits of PHB1 and PHB2. The mitochondrial prohibitin complex plays a role in a number of biological processes, including mitochondrial biogenesis and function, development, replicative senescence, and cell death.
mitochondrial proton-transporting ATP synthase complex A proton-transporting ATP synthase complex found in the mitochondrial membrane.
mitochondrial proton-transporting ATP synthase complex, catalytic sector F(1) The catalytic sector of the mitochondrial hydrogen-transporting ATP synthase; it comprises the catalytic core and central stalk, and is peripherally associated with the mitochondrial inner membrane when the entire ATP synthase is assembled.
mitochondrial proton-transporting ATP synthase complex, coupling factor F(o) All non-F1 subunits of the mitochondrial hydrogen-transporting ATP synthase, including integral and peripheral mitochondrial inner membrane proteins.
mitochondrial proton-transporting ATP synthase, catalytic core The hexamer, comprising three alpha and three beta subunits, that possesses the catalytic activity of the mitochondrial hydrogen-transporting ATP synthase.
mitochondrial proton-transporting ATP synthase, stator stalk
mitochondrial respiratory chain complex I A protein complex located in the mitochondrial inner membrane that forms part of the mitochondrial respiratory chain. It contains about 25 different polypeptide subunits, including NADH dehydrogenase (ubiquinone), flavin mononucleotide and several different iron-sulfur clusters containing non-heme iron. The iron undergoes oxidation-reduction between Fe(II) and Fe(III), and catalyzes proton translocation linked to the oxidation of NADH by ubiquinone.
mitochondrial respiratory chain complex II, succinate dehydrogenase complex (ubiquinone) A protein complex located in the mitochondrial inner membrane that forms part of the mitochondrial respiratory chain. Contains the four polypeptide subunits of succinate dehydrogenase, flavin-adenine dinucleotide and iron-sulfur. Catalyzes the oxidation of succinate by ubiquinone. Connects the TCA cycle with the respiratory chain.
mitochondrial respiratory chain complex III A protein complex located in the mitochondrial inner membrane that forms part of the mitochondrial respiratory chain. Contains about 10 polypeptide subunits including four redox centers: cytochrome b/b6, cytochrome c1 and an 2Fe-2S cluster. Catalyzes the oxidation of ubiquinol by oxidized cytochrome c1.
mitochondrial respiratory chain complex IV A protein complex located in the mitochondrial inner membrane that forms part of the mitochondrial respiratory chain. Contains the 13 polypeptide subunits of cytochrome c oxidase, including cytochrome a and cytochrome a3. Catalyzes the oxidation of reduced cytochrome c by dioxygen (O2).
mitochondrial ribosome A ribosome found in the mitochondrion of a eukaryotic cell; contains a characteristic set of proteins distinct from those of cytosolic ribosomes.
mitochondrion-derived vesicle
mitotic spindle A spindle that forms as part of mitosis. Mitotic and meiotic spindles contain distinctive complements of proteins associated with microtubules.
mitotic spindle astral microtubule
mitotic spindle microtubule
MLL1 complex A protein complex that can methylate lysine-4 of histone H3. MLL1/MLL is the catalytic methyltransferase subunit, and the complex also contains the core components ASH2L, HCFC1/HCF1 WDR5 and RBBP5.
MLL1/2 complex A protein complex that can methylate lysine-4 of histone H3, and which contains either of the protein subunits MLL1 or MLL2 in human, or equivalent in other species.
MLL3/4 complex A protein complex that can methylate lysine-4 of histone H3, and which contains either of the protein subunits MLL3 or MLL4 in mammals, or equivalent in other species.
monoatomic ion channel complex A protein complex that spans a membrane and forms a water-filled channel across the phospholipid bilayer allowing selective ion transport down its electrochemical gradient.
monomeric IgA immunoglobulin complex A protein complex composed of two identical immunoglobulin heavy chains of an IgA isotype and two identical immunoglobulin light chains, held together by disulfide bonds, and present in the extracellular space, in mucosal areas or other tissues, or circulating in the blood or lymph.
motile cilium A cilium which has a variable arrangement of axonemal microtubules, contains molecular motors, and beats with a characteristic whip-like pattern that promotes cell motility or transport of fluids and other cells across a cell surface. Motile cilia are typically found in multiple copies on epithelial cells that line the lumenal ducts of various tissues. Motile cilia may also function as sensory organelles.
MOZ/MORF histone acetyltransferase complex A histone acetyltransferase complex that has histone H3 acetyltransferase and coactivator activities. Subunits of the human complex include MYST3/MOZ, MYST4/MORF, ING5, EAF6 and one of BRPF1, BRD1/BRPF2 and BRPF3.
MPP7-DLG1-LIN7 complex A heterotrimeric protein complex formed by the association of MMP7, DLG1 and either LIN7A or LIN7C; regulates the stability and localization of DLG1 to cell junctions.
mRNA cleavage and polyadenylation specificity factor complex A multisubunit complex that binds to the canonical AAUAAA hexamer and to U-rich upstream sequence elements on the pre-mRNA, thereby stimulating the otherwise weakly active and nonspecific polymerase to elongate efficiently RNAs containing a poly(A) signal.
mRNA cleavage stimulating factor complex A protein complex required for mRNA cleavage but not for poly(A) addition.
MSL complex A histone acetyltransferase complex that catalyzes the acetylation of a histone H4 lysine residue at position 16. In human, it contains the catalytic subunit MOF, and MSL1, MSL2 and MSL3.
mucin granule A secretory granule that contains mucin.
multimeric ribonuclease P complex A ribonuclease P complex that generally contains a single RNA molecule and several protein molecules. Examples of this complex are found in Archaeal species.
multimerin complex
multivesicular body A type of late endosome in which regions of the limiting endosomal membrane invaginate to form internal vesicles; membrane proteins that enter the internal vesicles are sequestered from the cytoplasm.
multivesicular body lumen
multivesicular body membrane The lipid bilayer surrounding a multivesicular body.
multivesicular body, internal vesicle A membrane-bounded vesicle wholly contained within a multivesicular body.
multivesicular body, internal vesicle lumen The volume enclosed by the membrane of the multivesicular body internal vesicle.
muscle cell projection A prolongation or process extending from a muscle cell. A muscle cell is a mature contractile cell, commonly known as a myocyte. This cell has as part of its cytoplasm myofibrils organized in various patterns.
muscle cell projection membrane
muscle myosin complex A filament of myosin found in a muscle cell of any type.
muscle tendon junction A cell-substrate junction found at the terminal anchorage site of skeletal muscle cells to tendons.
Myc-Max complex A transcription factor complex that consists of a heterodimer of the bHLH-ZIP proteins Myc and Max.
myofibril The contractile element of skeletal and cardiac muscle; a long, highly organized bundle of actin, myosin, and other proteins that contracts by a sliding filament mechanism.
myosin filament A protein complex containing myosin heavy chains, plus associated light chains and other proteins, in which the myosin heavy chains are arranged into a filament.
myosin II filament A bipolar filament composed of myosin II molecules.
myosin V complex A myosin complex containing a dimer of class V myosin heavy chains and associated light chains; involved in intracellular transport. Myosin V is a dimeric molecule consisting of conserved motor domains followed by 6 IQ motifs which bind specific light chains and calmodulin. The tail domain is important for cellular localization and cargo binding and can be divided into an alpha-helical coiled coil region and a C-terminal globular region.
NADPH oxidase complex A enzyme complex of which the core is a heterodimer composed of a light (alpha) and heavy (beta) chain, and requires several other water-soluble proteins of cytosolic origin for activity. Functions in superoxide generation by the NADPH-dependent reduction of O2.
NatA complex A conserved complex that catalyzes the transfer of an acetyl group to an N-terminal Ser, Ala, Gly, or Thr residue of a protein acceptor molecule. In Saccharomyces the complex includes Nat1p and Ard1p, and may contain additional proteins.
NatB complex A conserved complex that catalyzes the transfer of an acetyl group to the N-terminal residue of a protein acceptor molecule that has a Met-Glu, Met-Asp, Met-Asn, or Met-Met N-terminus. In Saccharomyces the complex includes Nat3p and Mdm20p.
NatC complex A conserved complex that catalyzes the transfer of an acetyl group to the N-terminal residue of a protein acceptor molecule that has a Met-Ile, Met-Leu, Met-Trp, or Met-Phe N-terminus. In Saccharomyces the complex includes Mak3p, Mak10p, and Mak31p.
nBAF complex A SWI/SNF-type complex that is found in post-mitotic neurons, and in human contains actin and proteins encoded by the ARID1A/BAF250A or ARID1B/BAF250B, SMARCD1/BAF60A, SMARCD3/BAF60C, SMARCA2/BRM/BAF190B, SMARCA4/BRG1/BAF190A, SMARCB1/BAF47, SMARCC1/BAF155, SMARCE1/BAF57, SMARCC2/BAF170, DPF1/BAF45B, DPF3/BAF45C, ACTL6B/BAF53B genes. The nBAF complex along with CREST plays a role regulating the activity of genes essential for dendrite growth.
negative cofactor 2 complex A heterodimeric protein complex that can stably associate with TATA-binding protein on promoters, thereby preventing the assembly of transcription factors TFIIA and TFIIB and leading to repression of RNA polymerase II transcription. The two subunits, NC2alpha (Drap1) and NC2beta (Dr1), dimerize through histone fold domains of the H2A/H2B type present in the amino termini.
NELF complex A complex of five proteins, designated NELF-A, -B, -C, -D, and -E in human, that can physically associate with RNP polymerase II to induce transcriptional pausing.
neurofibrillary tangle Intracellular knot or clump of neurofibrils seen in the cerebral cortex in Alzheimer's disease.
neurofilament cytoskeleton Intermediate filament cytoskeletal structure that is made up of neurofilaments. Neurofilaments are specialized intermediate filaments found in neurons.
neuromuscular junction The junction between the axon of a motor neuron and a muscle fiber. In response to the arrival of action potentials, the presynaptic button releases molecules of neurotransmitters into the synaptic cleft. These diffuse across the cleft and transmit the signal to the postsynaptic membrane of the muscle fiber, leading to a change in post-synaptic potential.
neuron projection A prolongation or process extending from a nerve cell, e.g. an axon or dendrite.
neuron projection cytoplasm
neuron spine A small membranous protrusion, often ending in a bulbous head and attached to the neuron by a narrow stalk or neck.
neuron to neuron synapse
neuronal dense core vesicle
neuronal dense core vesicle lumen
neuronal dense core vesicle membrane
neuronal ribonucleoprotein granule A ribonucleoprotein complex that is found in the cytoplasm of axons and dendrites, and transports translationally silenced mRNAs to dendritic synapses, where they are released and translated in response to specific exogenous stimuli.
neurotransmitter receptor complex
NF-kappaB p50/p65 complex A heterodimer of NF-kappa B p50 and p65 subunits.
nitric-oxide synthase complex
NMDA selective glutamate receptor complex An assembly of four or five subunits which form a structure with an extracellular N-terminus and a large loop that together form the ligand binding domain. The C-terminus is intracellular. The ionotropic glutamate receptor complex itself acts as a ligand gated ion channel; on binding glutamate, charged ions pass through a channel in the center of the receptor complex. NMDA receptors are composed of assemblies of NR1 subunits (Figure 3) and NR2 subunits, which can be one of four separate gene products (NR2A-D). Expression of both subunits are required to form functional channels. The glutamate binding domain is formed at the junction of NR1 and NR2 subunits. NMDA receptors are permeable to calcium ions as well as being permeable to other ions. Thus NMDA receptor activation leads to a calcium influx into the post-synaptic cells, a signal thought to be crucial for the induction of NMDA-receptor dependent LTP and LTD.
Noc1p-Noc2p complex A heterodimer associated with 90S and 66S preribosomes. Predominantly, but not exclusively, nucleolar; involved in ribosomal large subunit biogenesis.
Noc2p-Noc3p complex
Noc4p-Nop14p complex A heterodimer associated with precursors of the eukaryotic small ribosomal subunit, including the 90S preribosome; involved in small subunit biogenesis.
non-motile cilium
NoRC complex An ISWI complex that contains an ATPase subunit of the ISWI family (specifically SNF2H in mammals, which contain two ISWI homologs) and a Tip5 homolog. In mammals, NoRC is involved in regulation of transcription from RNAP I and RNA polymerase III promoters.
npBAF complex A SWI/SNF-type complex that is found in neural stem or progenitor cells, and in human contains actin and proteins encoded by the ARID1A/BAF250A or ARID1B/BAF250B, SMARCD1/BAF60A, SMARCD3/BAF60C, SMARCA2/BRM/BAF190B, SMARCA4/BRG1/BAF190A, SMARCB1/BAF47, SMARCC1/BAF155, SMARCE1/BAF57, SMARCC2/BAF170, PHF10/BAF45A, ACTL6A/BAF53A genes. The npBAF complex is essential for the self-renewal/proliferative capacity of the multipotent neural stem cells.
NSL complex A histone acetyltransferase complex that catalyzes the acetylation of a histone H4 lysine residues at several positions. In human, it contains the catalytic subunit MOF, NSL1/KIAA1267, NSL2/KANSL2, NSL3/KANSL3, MCRS1, PHF20, OGT1, WDR5 and HCF1.
NuA4 histone acetyltransferase complex A complex having histone acetylase activity on chromatin, as well as ATPase, DNA helicase and structural DNA binding activities. The complex is thought to be involved in double-strand DNA break repair. Subunits of the human complex include HTATIP/TIP60, TRRAP, RUVBL1, BUVBL2, beta-actin and BAF53/ACTL6A. In yeast, the complex has 13 subunits, including the catalytic subunit Esa1 (homologous to human Tip60).
nuclear chromosome A chromosome found in the nucleus of a eukaryotic cell.
nuclear envelope lumen The region between the two lipid bilayers of the nuclear envelope; 20-40 nm wide.
nuclear inclusion body An intranuclear focus at which aggregated proteins have been sequestered.
nuclear inner membrane The inner, i.e. lumen-facing, lipid bilayer of the nuclear envelope.
nuclear lumen The volume enclosed by the nuclear inner membrane.
nuclear membrane Either of the lipid bilayers that surround the nucleus and form the nuclear envelope; excludes the intermembrane space.
nuclear microtubule Any microtubule in the nucleus of a cell.
nuclear outer membrane The outer, i.e. cytoplasm-facing, lipid bilayer of the nuclear envelope; continuous with the endoplasmic reticulum of the cell and sometimes studded with ribosomes.
nuclear stress granule A dense aggregation in the nucleus composed of proteins and RNAs that appear when the cell is under stress.
nucleolar exosome (RNase complex)
nucleolus A small, dense body one or more of which are present in the nucleus of eukaryotic cells. It is rich in RNA and protein, is not bounded by a limiting membrane, and is not seen during mitosis. Its prime function is the transcription of the nucleolar DNA into 45S ribosomal-precursor RNA, the processing of this RNA into 5.8S, 18S, and 28S components of ribosomal RNA, and the association of these components with 5S RNA and proteins synthesized outside the nucleolus. This association results in the formation of ribonucleoprotein precursors; these pass into the cytoplasm and mature into the 40S and 60S subunits of the ribosome.
nucleotide-excision repair factor 1 complex One of several protein complexes involved in nucleotide-excision repair; possesses DNA damage recognition and endodeoxynuclease activities. In S. cerevisiae, it is composed of Rad1p, Rad10p, and Rad14p; in human the subunits are ERCC4/XPF, ERCC1 and XPA, respectively.
nucleotide-excision repair factor 2 complex One of several protein complexes involved in nucleotide-excision repair; possesses damaged DNA binding activity. In S. cerevisiae, it is composed of Rad4p and Rad23p.
nucleotide-excision repair factor 3 complex One of several protein complexes involved in nucleotide-excision repair; possesses endodeoxynuclease and DNA helicase activities. In S. cerevisiae, it is composed of Rad2p and the core TFIIH-Ssl2p complex (core TFIIH is composed of Rad3p, Tfb1p, Tfb2p, Ssl1p, Tfb4p and Tfb5p. Note that Ssl2p is also called Rad25p).
nucleus A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent.
NURF complex An ISWI complex that contains an ATPase subunit of the ISWI family (SNF2L in mammals), a NURF301 homolog (BPTF in humans), and additional subunits, though the composition of these additional subunits varies slightly with species. NURF is involved in regulation of transcription from TRNA polymerase II promoters.
oligosaccharyltransferase I complex
oligosaccharyltransferase III complex
omegasome membrane
oncostatin-M receptor complex A heterodimeric receptor for the cytokine oncostatin-M (OSM). In humans the receptor complex is made up of the gene products gp130 and OSMR-beta.
organelle envelope lumen The region between the inner and outer lipid bilayers of an organelle envelope.
organelle inner membrane The inner, i.e. lumen-facing, lipid bilayer of an organelle envelope; usually highly selective to most ions and metabolites.
organelle outer membrane The outer, i.e. cytoplasm-facing in a cellular organelle, lipid bilayer of an organelle envelope.
outer acrosomal membrane The acrosomal membrane region that underlies the plasma membrane of the sperm. This membrane fuses with the sperm plasma membrane as part of the acrosome reaction.
outer dense fiber Structure or material found in the flagella of mammalian sperm that surrounds each of the nine microtubule doublets, giving a 9 + 9 + 2 arrangement rather than the 9 + 2 pattern usually seen. These dense fibers are stiff and noncontractile.
outer dynein arm Outer arm structure present on the outer doublet microtubules of ciliary and flagellar axonemes. Outer dynein arms contain 2-3 heavy chains, two or more intermediate chains and a cluster of 4-8 light chains. Inner and outer dynein arms have different functions in the generation of microtubule-based motility.
oxoglutarate dehydrogenase complex A complex of multiple copies of three enzymatic components: oxoglutarate dehydrogenase (lipoamide) ; EC:1.2.4.2 (E1), dihydrolipoamide S-succinyltransferase ; EC:2.3.1.61 (E2) and dihydrolipoamide dehydrogenase ; EC:1.8.1.4 (E3); catalyzes the overall conversion of 2-oxoglutarate to succinyl-CoA and carbon dioxide (CO2).
P granule A small cytoplasmic, non-membranous RNA/protein complex aggregates in the primordial germ cells of many higher eukaryotes.
P-body A focus in the cytoplasm where mRNAs may become inactivated by decapping or some other mechanism. mRNA processing and binding proteins are localized to these foci.
P-TEFb complex A positive transcription elongation factor complex b that comprises two subunits; an example is the budding yeast complex containing Svg1p (also called Bur1p) and Bur2p.
palmitoyltransferase complex A protein complex with palmitoyltransferase activity.
PAM complex, Tim23 associated import motor Protein complex located on the matrix side of the mitochondrial inner membrane and associated with the presequence translocase complex; hydrolyzes ATP to provide the force to drive import of proteins into the mitochondrial matrix.
PAR polarity complex
parallel fiber A parallel fiber results from the bifurcation of a cerebellar granule cell axon in the molecular layer into two diametrically opposed branches, that are oriented parallel to the long axis of the folium.
parallel fiber to Purkinje cell synapse
paranodal junction A highly specialized cell-cell junction found in vertebrates, which forms between a neuron and a glial cell, and has structural similarity to Drosophila septate junctions. It flanks the node of Ranvier in myelinated nerve and electrically isolates the myelinated from unmyelinated nerve segments and physically separates the voltage-gated sodium channels at the node from the cluster of potassium channels underneath the myelin sheath.
Parkin-FBXW7-Cul1 ubiquitin ligase complex A ubiquitin ligase complex containing Parkin (PARK2), the F-box protein FBXW7 (also called SEL-10) and a cullin from the Cul1 subfamily; substrate specificity is conferred by the F-box protein.
PAS complex A class III phosphatidylinositol 3-kinase complex that contains a phosphatidylinositol-3-phosphate 5-kinase subunit (Fab1p in yeast; PIKfyve in mammals), a kinase activator, and a phosphatase, and may also contain additional proteins; it is involved in regulating the synthesis and turnover of phosphatidylinositol 3,5-bisphosphate. In mammals the complex is composed of PIKFYVE, FIG4 and VAC14. In yeast it is composed of Atg18p, Fig4p, Fab1p, Vac14p and Vac7p.
pentameric IgM immunoglobulin complex A circulating form of IgM consisting of a pentamer of IgM core units with a single J chain polypeptide.
pericentric heterochromatin Heterochromatin that is located adjacent to the CENP-A rich centromere 'central core' and characterized by the modified histone H3K9me3.
periciliary membrane compartment A membrane domain at the base of cilia and flagella that is enriched in endocytosis-associated proteins and vesicles and that appears to function in regulating ciliary membrane homeostasis.
perineuronal net A dense extracellular matrix (ECM) structure that forms around many neuronal cell bodies and dendrites late in development and is responsible for synaptic stabilization in the adult brain.
perinucleolar chromocenter A chromocenter adjacent to the nucleolus.
perisynaptic extracellular matrix
peroxisomal matrix The volume contained within the membranes of a peroxisome; in many cells the matrix contains a crystalloid core largely composed of urate oxidase.
peroxisomal membrane The lipid bilayer surrounding a peroxisome.
peroxisome A small organelle enclosed by a single membrane, and found in most eukaryotic cells. Contains peroxidases and other enzymes involved in a variety of metabolic processes including free radical detoxification, lipid catabolism and biosynthesis, and hydrogen peroxide metabolism.
phagocytic vesicle A membrane-bounded intracellular vesicle that arises from the ingestion of particulate material by phagocytosis.
phagocytic vesicle lumen The volume enclosed by the membrane of a phagocytic vesicle.
phagocytic vesicle membrane The lipid bilayer surrounding a phagocytic vesicle.
phagolysosome A membrane-bounded intracellular vesicle formed by maturation of an early phagosome following the ingestion of particulate material by phagocytosis; during maturation, phagosomes acquire markers of late endosomes and lysosomes.
phosphatidylinositol 3-kinase complex, class I A phosphatidylinositol 3-kinase complex that contains a catalytic and a regulatory subunit of a phosphatidylinositol 3-kinase (PI3K) enzyme, plus one or more adaptor proteins. Class I PI3Ks phosphorylate phosphatidylinositol [PI], phosphatidylinositol-4-phosphate [PI(4)P] and phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2], and are divided into subclasses A and B according to the type of adaptor subunit with which they associate. The class I PI3K subfamily of genes comprises members in vertebrates, worm and fly, but none in yeast.
phosphatidylinositol 3-kinase complex, class IA A class I phosphatidylinositol 3-kinase complex that possesses 1-phosphatidylinositol-4-phosphate 3-kinase activity; comprises a catalytic class IA phosphoinositide 3-kinase (PI3K) subunit and an associated SH2 domain-containing regulatory subunit that is a member of a family of related proteins often called p85 proteins. Through the interaction with the SH2-containing adaptor subunits, Class IA PI3K catalytic subunits are linked to tyrosine kinase signaling pathways.
phosphatidylinositol 3-kinase complex, class IB A class I phosphatidylinositol 3-kinase complex that possesses 1-phosphatidylinositol-4-phosphate 3-kinase activity; comprises a catalytic class IB phosphoinositide 3-kinase (PI3K) subunit and an associated regulatory subunit that is larger than, and unrelated to, the p85 proteins present in class IA complexes. Class IB PI3Ks are stimulated by G-proteins and do not interact with the SH2-domain containing adaptors that bind to Class IA PI3Ks.
phosphatidylinositol 3-kinase complex, class III A phosphatidylinositol 3-kinase complex that contains a catalytic class III phosphoinositide 3-kinase (PI3K) subunit bound to a regulatory (adaptor) subunit. Additional adaptor proteins may be present. Class III PI3Ks have a substrate specificity restricted to phosphatidylinositol (PI).
phosphatidylinositol 3-kinase complex, class III, type I A class III phosphatidylinositol 3-kinase complex that is involved in autophagy. In budding yeast, this complex consists of Vps30p, Vps34p, Apg14p and Vps15p.
phosphatidylinositol 3-kinase complex, class III, type II A class III phosphatidylinositol 3-kinase complex that is involved in vacuolar protein sorting (VPS) via endosomes. In budding yeast, this complex consists of Vps30p, Vps34p, Vps38 and Vps15p.
photoreceptor cell cilium
pi-body A P granule that contains the PIWIL2-TDRD1 module, a set of proteins that act in the primary piRNA pathway. The pi-body corresponds to the cementing material between mitochondria found in gonocytes.
Piccolo NuA4 histone acetyltransferase complex A heterotrimeric H4/H2A histone acetyltransferase complex with a substrate preference of chromatin over free histones. It contains a subset of the proteins found in the larger NuA4 histone acetyltransferase complex; for example, the S. cerevisiae complex contains Esa1p, Yng2p, and Epl1p.
pigment granule A small, subcellular membrane-bounded vesicle containing pigment and/or pigment precursor molecules. Pigment granule biogenesis is poorly understood, as pigment granules are derived from multiple sources including the endoplasmic reticulum, coated vesicles, lysosomes, and endosomes.
pigment granule membrane
pinosome A membrane-bounded, uncoated intracellular vesicle formed by the process of pinocytosis.
piP-body A P granule that contains the PIWIL4-TDRD9 module, a set of proteins that act in the secondary piRNA pathway.
plasma membrane bounded cell projection cytoplasm All of the contents of a cell projection, excluding the plasma membrane surrounding the projection.
plasma membrane proton-transporting V-type ATPase complex
plasma membrane raft A membrane raft that is part of the plasma membrane.
platelet alpha granule A secretory organelle found in blood platelets, which is unique in that it exhibits further compartmentalization and acquires its protein content via two distinct mechanisms: (1) biosynthesis predominantly at the megakaryocyte (MK) level (with some vestigial platelet synthesis) (e.g. platelet factor 4) and (2) endocytosis and pinocytosis at both the MK and circulating platelet levels (e.g. fibrinogen (Fg) and IgG).
platelet alpha granule lumen The volume enclosed by the membrane of the platelet alpha granule.
platelet alpha granule membrane The lipid bilayer surrounding the platelet alpha granule.
platelet dense granule Electron-dense granule occurring in blood platelets that stores and secretes adenosine nucleotides and serotonin. They contain a highly condensed core consisting of serotonin, histamine, calcium, magnesium, ATP, ADP, pyrophosphate and membrane lysosomal proteins.
platelet dense granule lumen
platelet dense granule membrane The lipid bilayer surrounding the platelet dense granule.
platelet dense tubular network A network of membrane-bounded compartments found in blood platelets, where they regulate platelet activation by sequestering or releasing calcium. The dense tubular network exists as thin elongated membranes in resting platelets, and undergoes a major ultrastructural change, to a rounded vesicular form, upon addition of thrombin.
platelet dense tubular network membrane The lipid bilayer surrounding the platelet dense tubular network.
plus-end kinesin complex Any complex that includes a dimer of molecules from the kinesin superfamily and any associated proteins, and moves towards the plus end of a microtubule.
podocyte foot
podosome An actin-rich adhesion structure characterized by formation upon cell substrate contact and localization at the substrate-attached part of the cell, contain an F-actin-rich core surrounded by a ring structure containing proteins such as vinculin and talin, and have a diameter of 0.5 mm.
polymeric cytoskeletal fiber
polymeric IgA immunoglobulin complex A protein complex composed of two, three, or four monomeric IgA immunoglobulin complexes linked through both direct disulfide bonds and through disulfide binded monomers of J chain acting as a bridge. Each IgA monomer consists of two identical immunoglobulin heavy chains of an IgA isotype and two identical immunoglobulin light chains, held together by disulfide bonds. Dimeric IgA is sometimes complexed additionally with secretory component, and present in the extracellular space, in mucosal areas or other tissues, or circulating in the blood or lymph.
polysomal ribosome A ribosome bound to mRNA that forms part of a polysome.
polytene chromosome A type of chromosome in a polyploid cell, formed when multiple copies of homologous chromosomes are aligned side by side to give a giant chromosome in which distinct chromosome bands are readily visible.
post-mRNA release spliceosomal complex A spliceosomal complex that is formed following the release of the spliced product from the post-spliceosomal complex and contains the excised intron and three snRNPs, including U5.
post-spliceosomal complex A spliceosomal complex that is formed following the second splicing event and contains the spliced product, the excised intron, and three snRNPs, including U5.
postsynaptic actin cytoskeleton
postsynaptic density The postsynaptic density is a region that lies adjacent to the cytoplasmic face of the postsynaptic membrane at excitatory synapse. It forms a disc that consists of a range of proteins with different functions, some of which contact the cytoplasmic domains of ion channels in the postsynaptic membrane. The proteins making up the disc include receptors, and structural proteins linked to the actin cytoskeleton. They also include signalling machinery, such as protein kinases and phosphatases. The postsynaptic density may be part of a neuron or a muscle cell or a glial cell.
postsynaptic density membrane
postsynaptic early endosome
postsynaptic early endosome membrane
postsynaptic intermediate filament cytoskeleton
postsynaptic recycling endosome
postsynaptic specialization membrane
potassium channel complex An ion channel complex through which potassium ions pass.
potassium ion-transporting ATPase complex Protein complex that carries out the reaction: ATP + H2O + K+(out) = ADP + phosphate + K+(in). It is a high affinity potassium uptake system. The E. coli complex consists of 4 proteins: KdpA is the potassium ion translocase, KdpB is the ATPase, and KdpC and KdpF seem to be involved in assembly and stabilization of the complex.
potassium:proton exchanging ATPase complex A protein complex that possesses hydrogen:potassium-exchanging ATPase activity; characterized in animal cells, where it maintains ionic gradients of K+ at the expense of ATP hydrolysis; The complex contains two obligatory subunits, the catalytic alpha subunit and a glycosylated beta subunit; two additional subunits, gamma and channel-inducing factor (CHIF), may also be present.
PR-DUB complex A multimeric protein complex that removes monoubiquitin from histone H2A. In Drosophila and mammals, the core of the complex is composed of Calypso/BAP1 and Asx/ASXL1, respectively.
PRC1 complex A multiprotein complex that mediates monoubiquitination of lysine residues of histone H2A (lysine-118 in Drosophila or lysine-119 in mammals). The complex is required for stable long-term maintenance of transcriptionally repressed states and is involved in chromatin remodeling.
precatalytic spliceosome A spliceosomal complex that is formed by the recruitment of a preassembled U5-containing tri-snRNP to the prespliceosome. Although all 5 snRNPs are present, the precatalytic spliceosome is catalytically inactive. The precatalytic spliceosome includes many proteins in addition to those found in the associated snRNPs.
preribosome, large subunit precursor A preribosomal complex consisting of 27SA, 27SB, and/or 7S pre-rRNA, 5S rRNA, ribosomal proteins including late-associating large subunit proteins, and associated proteins; a precursor of the eukaryotic cytoplasmic large ribosomal subunit.
preribosome, small subunit precursor A preribosomal complex consisting of 20S pre-rRNA, ribosomal proteins including late-associating small subunit proteins, and associated proteins; a precursor of the eukaryotic cytoplasmic small ribosomal subunit.
prespliceosome A spliceosomal complex that is formed by association of the 5' splice site and the branch point sequence with specific snRNPs. The prespliceosome includes many proteins in addition to those found in the bound snRNPs. Commitment to a given pair of 5' and 3' splice sites occurs at the time of prespliceosome formation. Prespliceosome complexes are not active for splicing, but are instead an early step in the assembly of a spliceosomal complex.
presynaptic intermediate filament cytoskeleton
primary dendrite
primary lysosome A lysosome before it has fused with a vesicle or vacuole.
prominosome An extracellular membrane-bounded vesicle that contains prominin proteins (in mouse Prom1/CD33 or Prom2) and are found in body fluids including ventricular fluid, saliva, urine and seminal fluid. In the ventricular fluid of the developing mouse brain two major classes of these particles have been observed (P2 particles of 500-1000 nm and P4 particles of 50-80 nm) which likely originate from microvilli, primary cilia and/or the midbody of neuroepithelial cells. The physiological role is not known.
pronucleus The nucleus of either the ovum or the spermatozoon following fertilization. Thus, in the fertilized ovum, there are two pronuclei, one originating from the ovum, the other from the spermatozoon that brought about fertilization; they approach each other, but do not fuse until just before the first cleavage, when each pronucleus loses its membrane to release its contents.
protein C inhibitor-coagulation factor V complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and coagulation factor V (F5); formation of the complex inhibits the serine protease activity of coagulation factor V.
protein C inhibitor-coagulation factor Xa complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and coagulation factor Xa (F10); formation of the complex inhibits the serine protease activity of coagulation factor Xa.
protein C inhibitor-coagulation factor XI complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and coagulation factor XI (F11); formation of the complex inhibits the serine protease activity of coagulation factor XI.
protein C inhibitor-KLK3 complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and prostate-specific antigen (KLK3); formation of the complex inhibits the serine protease activity of prostate-specific antigen.
protein C inhibitor-plasma kallikrein complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and plasma kallikrein (KLK1B); formation of the complex inhibits the serine protease activity of plasma kallikrein.
protein C inhibitor-PLAT complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and tissue-type plasminogen activator (PLAT); formation of the complex inhibits the serine protease activity of tissue-type plasminogen activator.
protein C inhibitor-PLAU complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and urokinase-type plasminogen activator (PLAU); formation of the complex inhibits the serine protease activity of urokinase-type plasminogen activator.
protein C inhibitor-thrombin complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and thrombin (F2); formation of the complex inhibits the serine protease activity of thrombin.
protein C inhibitor-TMPRSS11E complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and transmembrane protease serine 11E (TMPRSS11E); formation of the complex inhibits the serine protease activity of transmembrane protease serine 11E.
protein C inhibitor-TMPRSS7 complex A heterodimeric protein complex that contains protein C inhibitor (SERPINA5) and transmembrane protease serine 7 (TMPRSS7); formation of the complex inhibits the serine protease activity of transmembrane protease serine 7.
protein kinase 5 complex A protein complex that activates cyclin-dependent kinase 5; composed of regulatory and catalytic subunits.
protein kinase complex A protein complex which is capable of protein kinase activity.
protein phosphatase 4 complex The complex formed by the catalytic subunit of protein phosphatase 4 plus a regulatory subunit.
protein phosphatase type 2A complex A protein complex that has protein serine/threonine phosphatase activity that is polycation-stimulated (PCS), being directly stimulated by protamine, polylysine, or histone H1; it constitutes a subclass of several enzymes activated by different histones and polylysine, and consists of catalytic, scaffolding, and regulatory subunits. The catalytic and scaffolding subunits form the core enzyme, and the holoenzyme also includes the regulatory subunit.
protein serine/threonine phosphatase complex A complex, normally consisting of a catalytic and a regulatory subunit, which catalyzes the removal of a phosphate group from a serine or threonine residue of a protein.
proton-transporting ATP synthase complex A proton-transporting two-sector ATPase complex that catalyzes the phosphorylation of ADP to ATP during oxidative phosphorylation. The complex comprises a membrane sector (F0) that carries out proton transport and a cytoplasmic compartment sector (F1) that catalyzes ATP synthesis by a rotational mechanism; the extramembrane sector (containing 3 a and 3 b subunits) is connected via the d-subunit to the membrane sector by several smaller subunits. Within this complex, the g and e subunits and the 9-12 c subunits rotate by consecutive 120 degree angles and perform parts of ATP synthesis. This movement is driven by the hydrogen ion electrochemical potential gradient.
proton-transporting V-type ATPase complex A proton-transporting two-sector ATPase complex that couples ATP hydrolysis to the transport of protons across a concentration gradient. The resulting transmembrane electrochemical potential of H+ is used to drive a variety of (i) secondary active transport systems via H+-dependent symporters and antiporters and (ii) channel-mediated transport systems. The complex comprises a membrane sector (V0) that carries out proton transport and a cytoplasmic compartment sector (V1) that catalyzes ATP hydrolysis. V-type ATPases are found in the membranes of organelles such as vacuoles, endosomes, and lysosomes, and in the plasma membrane.
proton-transporting V-type ATPase, V0 domain A protein complex that forms part of a proton-transporting V-type ATPase and mediates proton transport across a membrane. The V0 complex consists of at least four different subunits (a,c,d and e); six or more c subunits form a proton-binding rotor ring.
proton-transporting V-type ATPase, V1 domain A protein complex that forms part of a proton-transporting V-type ATPase and catalyzes ATP hydrolysis. The V1 complex consists of: (1) a globular headpiece with three alternating copies of subunits A and B that form a ring, (2) a central rotational stalk composed of single copies of subunits D and F, and (3) a peripheral stalk made of subunits C, E, G and H. Subunits A and B mediate the hydrolysis of ATP at three reaction sites associated with subunit A.
proximal dendrite
proximal neuron projection
pseudopodium A temporary cytoplasmic extrusion by means of which an ameba or other ameboid organism or cell moves about or engulfs food.
PTW/PP1 phosphatase complex A protein serine/threonine phosphatase complex that contains a catalytic subunit (PPP1CA, PPP1CB or PPP1CC) and the regulatory subunits PPP1R10 (PNUTS), TOX4 and WDR82, and plays a role in the control of chromatin structure and cell cycle progression during the transition from mitosis into interphase.
Rad6-Rad18 complex
Rb-E2F complex A multiprotein complex containing a heterodimeric E2F transcription factor and a Retinoblastoma (Rb) family member. This complex is capable of repressing transcription of E2F-regulated genes in order to regulate cell cycle progression.
rDNA heterochromatin A region of heterochromatin located at the rDNA repeats in a chromosome.
recycling endosome Organelle consisting of networks of 60nm tubules organized around the microtubule organizing centre in some cell types. They transport molecules (e.g., receptors, transporters, lipids) derived from endosomes, the Golgi apparatus, or the cytoplasm to the plasma membrane. Transported molecules may be recycled for reuse, or may be newly synthesized.
recycling endosome lumen
recycling endosome membrane The lipid bilayer surrounding a recycling endosome.
respiratory chain complex I Respiratory chain complex I is an enzyme of the respiratory chain. It consists of several polypeptide chains and is L-shaped, with a horizontal arm lying in the membrane and a vertical arm that projects into the matrix. The electrons of NADH enter the chain at this complex.
respiratory chain complex III A protein complex that transfers electrons from ubiquinol to cytochrome c and translocates two protons across a membrane. The complex contains a core structure of three catalytic subunits: cytochrome b, the Rieske iron sulfur protein (ISP), and cytochrome c1, which are arranged in an integral membrane-bound dimeric complex; additional subunits are present, and vary among different species.
respiratory chain complex IV A part of the respiratory chain, containing the 13 polypeptide subunits of cytochrome c oxidase, including cytochrome a and cytochrome a3. Catalyzes the oxidation of reduced cytochrome c by dioxygen (O2).
ribonuclease MRP complex A ribonucleoprotein complex that contains an RNA molecule of the snoRNA family, and cleaves the rRNA precursor as part of rRNA transcript processing. It also has other roles: In S. cerevisiae it is involved in cell cycle-regulated degradation of daughter cell-specific mRNAs, while in mammalian cells it also enters the mitochondria and processes RNAs to create RNA primers for DNA replication.
ribose phosphate diphosphokinase complex A protein complex having ribose phosphate diphosphokinase activity.
ribosome An intracellular organelle, about 200 A in diameter, consisting of RNA and protein. It is the site of protein biosynthesis resulting from translation of messenger RNA (mRNA). It consists of two subunits, one large and one small, each containing only protein and RNA. Both the ribosome and its subunits are characterized by their sedimentation coefficients, expressed in Svedberg units (symbol: S). Hence, the prokaryotic ribosome (70S) comprises a large (50S) subunit and a small (30S) subunit, while the eukaryotic ribosome (80S) comprises a large (60S) subunit and a small (40S) subunit. Two sites on the ribosomal large subunit are involved in translation, namely the aminoacyl site (A site) and peptidyl site (P site). Ribosomes from prokaryotes, eukaryotes, mitochondria, and chloroplasts have characteristically distinct ribosomal proteins.
Ric1-Rgp1 guanyl-nucleotide exchange factor complex A protein complex that acts as a nucleotide exchange factor for the GTPase Ypt6p, and is required for fusion of endosome-derived vesicles with the Golgi.
RISC complex A ribonucleoprotein complex that contains members of the Argonaute family of proteins, small interfering RNAs (siRNAs) or microRNAs (miRNAs), and miRNA or siRNA-complementary mRNAs, in addition to a number of accessory factors. The RISC complex is involved in posttranscriptional repression of gene expression through downregulation of translation or induction of mRNA degradation.
RISC-loading complex A trimeric ribonucleoprotein complex that and is required for the formation of a mature RNA induced silencing complex (RISC). In humans the complex is composed of the endonuclease Dicer (DICER1) and TRBP (TARBP2) in association with the Argonaute protein Ago2 (EIF2C2/AGO2). Within the complex, Dicer and TRBP are required to process precursor miRNAs (pre-miRNAs) to mature miRNAs and then load them onto Ago2. Ago2 bound to the mature miRNA constitutes the minimal RISC and may subsequently dissociate from Dicer and TRBP.
RNA N6-methyladenosine methyltransferase complex An mRNA methyltransferase complex that catalyzes the post-transcriptional methylation of adenosine to form N6-methyladenosine (m6A). In budding yeast, the MIS complex consists of Mum2p, Ime4p and Slz1p. In vertebrates, the complex consists of METTL3, METTL14 and WTAP.
RNA polymerase I complex RNA polymerase I, one of three nuclear DNA-directed RNA polymerases found in all eukaryotes, is a multisubunit complex; typically it produces rRNAs. Two large subunits comprise the most conserved portion including the catalytic site and share similarity with other eukaryotic and bacterial multisubunit RNA polymerases. The remainder of the complex is composed of smaller subunits (generally ten or more), some of which are also found in RNA polymerase III and others of which are also found in RNA polymerases II and III. Although the core is competent to mediate ribonucleic acid synthesis, it requires additional factors to select the appropriate template.
RNA polymerase I core factor complex A RNA polymerase I-specific transcription factor complex that is required for the transcription of rDNA by RNA polymerase I. In yeast the complex consists of Rrn6p, Rrn7p, and Rrn11p.
RNA polymerase II, core complex RNA polymerase II, one of three nuclear DNA-directed RNA polymerases found in all eukaryotes, is a multisubunit complex; typically it produces mRNAs, snoRNAs, and some of the snRNAs. Two large subunits comprise the most conserved portion including the catalytic site and share similarity with other eukaryotic and bacterial multisubunit RNA polymerases. The largest subunit of RNA polymerase II contains an essential carboxyl-terminal domain (CTD) composed of a variable number of heptapeptide repeats (YSPTSPS). The remainder of the complex is composed of smaller subunits (generally ten or more), some of which are also found in RNA polymerases I and III. Although the core is competent to mediate ribonucleic acid synthesis, it requires additional factors to select the appropriate template.
RNA polymerase III complex RNA polymerase III, one of three nuclear DNA-directed RNA polymerases found in all eukaryotes, is a multisubunit complex; typically it produces 5S rRNA, tRNAs and some of the small nuclear RNAs. Two large subunits comprise the most conserved portion including the catalytic site and share similarity with other eukaryotic and bacterial multisubunit RNA polymerases. The remainder of the complex is composed of smaller subunits (generally ten or more), some of which are also found in RNA polymerase I and others of which are also found in RNA polymerases I and II. Although the core is competent to mediate ribonucleic acid synthesis, it requires additional factors to select the appropriate template.
RNA polymerase transcription factor SL1 complex A RNA polymerase I-specific transcription factor complex that contains the TATA-box-binding protein (TBP) and at least three TBP-associated factors including proteins known in mammals as TAFI110, TAFI63 and TAFI48.
RNA-directed RNA polymerase complex A protein complex that possesses RNA-directed RNA polymerase activity.
rod photoreceptor disc membrane
rough endoplasmic reticulum The rough (or granular) endoplasmic reticulum (ER) has ribosomes adhering to the outer surface; the ribosomes are the site of translation of the mRNA for those proteins which are either to be retained within the cisternae (ER-resident proteins), the proteins of the lysosomes, or the proteins destined for export from the cell. Glycoproteins undergo their initial glycosylation within the cisternae.
rough endoplasmic reticulum lumen The volume enclosed by the membranes of the rough endoplasmic reticulum.
rough endoplasmic reticulum membrane The lipid bilayer surrounding the rough endoplasmic reticulum.
RSC-type complex A protein complex similar to, but more abundant than, the Swi/Snf complex. The RSC complex is generally recruited to RNA polymerase III promoters and is specifically recruited to RNA polymerase II promoters by transcriptional activators and repressors; it is also involved in non-homologous end joining.
RSF complex An ISWI complex that contains an ATPase subunit of the ISWI family (SNF2H in mammals) and an RSF1 homolog. It mediates nucleosome deposition and generates regularly spaced nucleosome arrays. In mammals, RSF is involved in regulation of transcription from RNA polymerase II promoters).
SAGA complex A SAGA-type histone acetyltransferase complex that contains Spt8 (in budding yeast) or a homolog thereof; additional polypeptides include Spt group, consisting of Spt7, Spt3, and Spt20/Ada5, which interact with the TATA-binding protein (TBP); the Ada group, consisting of Ada1, Ada2, Ada3, Ada4/Gcn5, and Ada5/Spt20, which is functionally linked to the nucleosomal HAT activity; Tra1, an ATM/PI-3 kinase-related protein that targets DNA-bound activators for recruitment to promoters; the TBP-associated factor (TAF) proteins, consisting of Taf5, Taf6, Taf9, Taf10, and Taf12, which mediate nucleosomal HAT activity and are thought to help recruit the basal transcription machinery.
SAGA-type complex A histone acetyltransferase complex that acetylates nucleosomal H3 and H2B and is required for the expression of a subset of Pol II-transcribed genes. The budding yeast complex includes the acetyltransferase Gcn5p, several proteins of the Spt and Ada families, and several TBP-associate proteins (TAFs); analogous complexes in other species have analogous compositions, and usually contain homologs of the yeast proteins.
SAM complex A large complex of the mitochondrial outer membrane that mediates sorting of some imported proteins to the outer membrane and their assembly in the membrane; functions after import of incoming proteins by the mitochondrial outer membrane translocase complex.
sarcoglycan complex A protein complex formed of four sarcoglycans plus sarcospan; there are six known sarcoglycans: alpha-, beta-, gamma-, delta-, epsilon- and zeta-sarcoglycan; all are N-glycosylated single-pass transmembrane proteins. The sarcoglycan-sarcospan complex is a subcomplex of the dystrophin glycoprotein complex, and is fixed to the dystrophin axis by a lateral association with the dystroglycan complex.
sarcolemma The outer membrane of a muscle cell, consisting of the plasma membrane, a covering basement membrane (about 100 nm thick and sometimes common to more than one fiber), and the associated loose network of collagen fibers.
sarcoplasmic reticulum A fine reticular network of membrane-limited elements that pervades the sarcoplasm of a muscle cell; continuous over large portions of the cell and with the nuclear envelope; that part of the endoplasmic reticulum specialized for calcium release, uptake and storage.
sarcoplasmic reticulum lumen The volume enclosed by the membranes of the sarcoplasmic reticulum.
sarcoplasmic reticulum membrane The lipid bilayer surrounding the sarcoplasmic reticulum.
Scc2-Scc4 cohesin loading complex
SCF ubiquitin ligase complex A ubiquitin ligase complex in which a cullin from the Cul1 subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by a Skp1 adaptor and an F-box protein. SCF complexes are involved in targeting proteins for degradation by the proteasome. The best characterized complexes are those from yeast and mammals (with core subunits named Cdc53/Cul1, Rbx1/Hrt1/Roc1).
Schaffer collateral - CA1 synapse
Sec61 translocon complex A translocon complex that contains a core heterotrimer of conserved alpha, beta and gamma subunits, and may contain additional proteins (translocon-associated proteins or TRAPs); in budding yeast the core proteins are Sec61p, Sbh1p, and Sss1p. The Sec61 translocon complex functions in cotranslational and posttranslational translocation events.
secondary lysosome Vacuole formed by the fusion of a lysosome with an organelle (autosome) or with a primary phagosome.
secretory dimeric IgA immunoglobulin complex A dimeric form of secretory IgA immunoglobulin complex.
secretory granule lumen The volume enclosed by the membrane of a secretory granule.
secretory granule membrane The lipid bilayer surrounding a secretory granule.
secretory IgA immunoglobulin complex A polymeric IgA immunoglobulin complex that is complexed with one chain of secretory component (SC). Polymeric IgA is present in mucosal areas, having been transported via a transcytosis mechanism in mucosal epithelial cells relying on the polymeric Ig receptor, a portion of which then remains bound to the polymeric IgA as secretory component.
secretory vesicle
senescence-associated heterochromatin focus A transcriptionally-silent heterochromatin structure present in senescent cells. Contains the condensed chromatin of one chromosome and is enriched for histone modifications. Thought to repress expression of proliferation-promoting genes.
septin cytoskeleton The part of the cytoskeleton (the internal framework of a cell) composed of septins and associated proteins. Includes septin cytoskeleton-associated complexes.
septin ring A tight ring-shaped structure that forms in the division plane at the site of cytokinesis; composed of members of the conserved family of filament-forming proteins called septins as well as septin-associated proteins. This type of septin structure is observed at the bud neck of budding fungal cells, at the site of cell division in animal cells, at the junction between the mother cell and a pseudohyphal projection, and also within hyphae of filamentous fungi at sites where a septum will form.
serine C-palmitoyltransferase complex An enzyme complex that catalyzes the transfer of a palmitoyl on to serine, forming 3-dehydro-D-sphinganine.
serine protease inhibitor complex A heterodimeric protein complex that contains a serine protease inhibitor and a protease; formation of the complex inhibits serine protease activity.
serine-type endopeptidase complex
serine-type peptidase complex
serine/threonine protein kinase complex A protein complex which is capable of protein serine/threonine kinase activity.
serotonin-activated cation-selective channel complex
Set1C/COMPASS complex A conserved protein complex that catalyzes methylation of histone H3. In Saccharomyces the complex contains Shg1p, Sdc1p, Swd1p, Swd2p, Swd3p, Spp1p, Bre2p, and the trithorax-related Set1p; in mammals it contains the catalytic subunit (SETD1A or SETD1B), WDR5, WDR82, RBBP5, ASH2L/ASH2, CXXC1/CFP1, HCFC1 and DPY30.
sex chromatin Chromatin that is part of a sex chromosome.
sex chromosome A chromosome involved in sex determination.
Shc-EGFR complex A protein complex that contains the epidermal growth factor receptor (EGFR) and the adaptor protein Shc, and is involved in linking EGFR activation to the p21-Ras pathway.
sheet-forming collagen trimer sheet-forming collagen trimer
shelterin complex A nuclear telomere cap complex that is formed by the association of telomeric ssDNA- and dsDNA-binding proteins with telomeric DNA, and is involved in telomere protection and recruitment of telomerase. The complex contains TRF1, TRF2, POT1, RAP1, TIN2 and TPP1 in mammalian cells, and Pot1, Tpz1, Ccq1, Poz1, Rap1, Rif1, Rif2and Rap1 in Schizosaccharomyces. Taz1 and Rap1 (or their mammalian equivalents) form a dsDNA-binding subcomplex, Pot1 and Tpz1 form an ssDNA-binding subcomplex, and the two subcomplexes are bridged by Poz1.
signal recognition particle, endoplasmic reticulum targeting A ribonucleoprotein particle of 325 kDa composed of a 7S (300 nucleotide) RNA molecule and a complex of six different polypeptides. This binds both to the N-terminal signal peptide for proteins destined for the endoplasmic reticulum as they emerge from the large ribosomal subunit and also to the ribosome. This binding arrests further translation thereby preventing the proteins from being released into the cytosol. The SRP-ribosome complex then diffuses to the endoplasmic reticulum where it is bound to the signal recognition particle receptor, which allows resumption of protein synthesis and facilitates the passage of the growing polypeptide chain through the translocon. Through a process involving GTP hydrolysis, the SRP-SRP receptor complex dissociates and SRP returns to the cytosol. Of the six polypeptides of SRP the 54 kDa subunit (SRP54) is the central player. It contains an N-terminal GTPase domain and a C-terminal domain that binds directly to the signal peptide and the SRP RNA. Examples of this component are found in Mus musculus, Saccharomyces cerevisiae and Arabidopsis thaliana.
Sin3 complex A multiprotein complex that functions broadly in eukaryotic organisms as a transcriptional repressor of protein-coding genes, through the gene-specific deacetylation of histones. Amongst its subunits, the Sin3 complex contains Sin3-like proteins, and a number of core proteins that are shared with the NuRD complex (including histone deacetylases and histone binding proteins). The Sin3 complex does not directly bind DNA itself, but is targeted to specific genes through protein-protein interactions with DNA-binding proteins.
Sin3-type complex Any of a number of evolutionarily conserved histone deacetylase complexes (HDACs) containing a core consisting of a paired amphipathic helix motif protein (e.g. Sin3p in S. cerevisiae, Pst1 in S. pombe or Sin3A in mammals) at least one class I histone deacetylase (e.g. Rpd3p in S. cerevisiae, Clr6 in S. pombe, or HDAC1 and HDAC2 in mammals), and at least one WD40 repeat protein (e.g. Ume1p in S. cerevisiae, Prw1 in S. pombe, or RbAp46 and RbAp48 in mammals). These complexes also contain a variable number of other proteins that direct histone binding, DNA binding, or add other functionality to the complex.
slit diaphragm A specialized cell-cell junction found between the interdigitating foot processes of the glomerular epithelium (the podocytes) in the vertebrate kidney, which is adapted for facilitating glomerular filtration.
small ribosomal subunit The smaller of the two subunits of a ribosome.
small-subunit processome A large ribonucleoprotein complex that is an early preribosomal complex. In S. cerevisiae, it has a size of 80S and consists of the 35S pre-rRNA, early-associating ribosomal proteins most of which are part of the small ribosomal subunit, the U3 snoRNA and associated proteins.
Smc5-Smc6 complex A conserved complex that contains a heterodimer of SMC proteins (Smc5p and Smc6p, or homologs thereof) and several other proteins, and is involved in DNA repair and maintaining cell cycle arrest following DNA damage. In S. cerevisiae, this is an octameric complex called Mms21-Smc5-Smc6 complex, with at least five of its subunits conserved in fission yeast and humans.
smooth endoplasmic reticulum The smooth endoplasmic reticulum (smooth ER or SER) has no ribosomes attached to it. The smooth ER is the recipient of the proteins synthesized in the rough ER. Those proteins to be exported are passed to the Golgi complex, the resident proteins are returned to the rough ER and the lysosomal proteins after phosphorylation of their mannose residues are passed to the lysosomes. Glycosylation of the glycoproteins also continues. The smooth ER is the site of synthesis of lipids, including the phospholipids. The membranes of the smooth ER also contain enzymes that catalyze a series of reactions to detoxify both lipid-soluble drugs and harmful products of metabolism. Large quantities of certain compounds such as phenobarbital cause an increase in the amount of the smooth ER.
smooth endoplasmic reticulum membrane The lipid bilayer surrounding the smooth endoplasmic reticulum.
sodium channel complex An ion channel complex through which sodium ions pass.
sodium:potassium-exchanging ATPase complex Sodium:potassium-exchanging ATPases are tetrameric proteins, consisting of two large alpha subunits and two smaller beta subunits. The alpha subunits bear the active site and penetrate the membrane, while the beta subunits carry oligosaccharide groups and face the cell exterior.
sorting endosome A multivesicular body surrounded by and connected with multiple tubular compartments with associated vesicles.
specific granule Granule with a membranous, tubular internal structure, found primarily in mature neutrophil cells. Most are released into the extracellular fluid. Specific granules contain lactoferrin, lysozyme, vitamin B12 binding protein and elastase.
specific granule lumen
specific granule membrane The lipid bilayer surrounding a specific granule, a granule with a membranous, tubular internal structure, found primarily in mature neutrophil cells. Most are released into the extracellular fluid. Specific granules contain lactoferrin, lysozyme, vitamin B12 binding protein and elastase.
spectrin-associated cytoskeleton The part of the cytoskeleton composed of spectrin, protein 4.1 and ankyrin. Spectrin-associated cytoskeleton is associated with the plasma membrane.
sperm flagellum A microtubule-based flagellum (or cilium) that is part of a sperm, a mature male germ cell that develops from a spermatid.
sperm plasma membrane
spermatoproteasome complex A proteasome specifically found in mammalian testis. Contains the proteasome activator PA200 in the regulatory particle, and beta1i, beta2i, beta5i and/or alpha4s in the core (20S) subunit. Beta1i, beta2i and beta5i are inducible catalytic subunits, closely related to beta1, beta2 and beta5. Alpha4s is a sperm-specific 20S subunit, but unlike other alternative 20S subunits alpha4s lies in the outer alpha-ring and lacks catalytic activity.
spherical high-density lipoprotein particle A mature high-density lipoprotein (HDL) particle, converted from discoidal HDL particles following the esterification of cholesterol in the particle by phosphatidylcholine-sterol O-acyltransferase (lecithin cholesterol acyltransferase; LCAT).
spindle The array of microtubules and associated molecules that forms between opposite poles of a eukaryotic cell during mitosis or meiosis and serves to move the duplicated chromosomes apart.
spindle microtubule Any microtubule that is part of a mitotic or meiotic spindle; anchored at one spindle pole.
spliceosomal snRNP complex A ribonucleoprotein complex involved in formation of the spliceosome and composed of one or more snRNA and multiple protein components.
spliceosomal tri-snRNP complex A spliceosomal snRNP complex containing U4 and U6 (or U4atac and U6atac) snRNAs and U5 snRNAs and associated proteins.
spot adherens junction A small cell-cell adherens junction assembled during the cellularization stage of insect embyrogenesis; spot adherens junctions later fuse to form the zonula adherens.
SPOTS complex A multiprotein complex at least composed of serine palmitoyltransferases and ORM proteins (known as ORMDL proteins in mammals and other higher vertebrates) that plays a key role in sphingolipid homeostasis.
Ssh1 translocon complex A translocon complex that contains a core heterotrimer of alpha, beta and gamma subunits, and may contain additional proteins (translocon-associated proteins or TRAPs); in budding yeast the core proteins are Ssh1p, Sbh2p, and Sss1p. The Ssh1 translocon complex is involved in the cotranslational pathway of protein transport across the ER membrane, and recognizes proteins bearing strongly hydrophobic signal sequences.
succinate dehydrogenase complex (ubiquinone) The enzyme that catalyzes the oxidation of succinate and ubiquinone to fumarate and ubiquinol; involved in aerobic respiration, repressed in anaerobic respiration.
succinate-CoA ligase complex A heterodimeric enzyme complex, usually composed of an alpha and beta chain. Functions in the TCA cycle, hydrolyzing succinyl-CoA into succinate and CoA, thereby forming ATP or GTP.
succinate-CoA ligase complex (ADP-forming) A heterodimeric enzyme complex, composed of an alpha and beta chain, most usually found in (but not limited to) bacteria. Functions in the TCA cycle, hydrolyzing succinyl-CoA into succinate and CoA, thereby forming ATP.
succinate-CoA ligase complex (GDP-forming) A heterodimeric enzyme complex, usually composed of an alpha and beta chain. Functions in the TCA cycle, hydrolyzing succinyl-CoA into succinate and CoA, thereby forming GTP.
SUMO ligase complex
super elongation complex A heterodimeric protein complex that acts as an RNA polymerase II elongation factor; the complex is conserved from yeast to humans, and is present in S. pombe, but absent from S. cerevisiae.
supramolecular fiber
supraspliceosomal complex Multicomponent complex of RNA and proteins that is composed of four active spliceosomes, termed native spliceosomes, connected to each other by the pre-mRNA. The supraspliceosome is the nuclear machine where the pre-mRNA processing takes place, like the 5'-end capping, 3'-end cleavage, splicing and editing.
sweet taste receptor complex
SWI/SNF complex A SWI/SNF-type complex that contains nine or more proteins, including both conserved (core) and nonconserved components; the Swi2/Snf2 ATPase is one of the core components.
Swr1 complex A multisubunit protein complex that is involved in chromatin remodeling. It is required for the incorporation of the histone variant H2AZ into chromatin. In S. cerevisiae, the complex contains Swr1p, a Swi2/Snf2-related ATPase, and 12 additional subunits.
symmetric synapse A type of synapse occurring primarily on dendrite shafts and neuronal cell bodies. Symmetric synapses involve axons containing clusters of predominantly flattened or elongated vesicles and do not contain a prominent postsynaptic density.
symmetric, GABA-ergic, inhibitory synapse
synapse-associated extracellular matrix
synaptic membrane A specialized area of membrane on either the presynaptic or the postsynaptic side of a synapse, the junction between a nerve fiber of one neuron and another neuron or muscle fiber or glial cell.
synaptic vesicle membrane The lipid bilayer surrounding a synaptic vesicle.
synaptobrevin 2-SNAP-25-syntaxin-1a complex A SNARE complex that contains synaptobrevin 2 (VAMP2), SNAP-25, and syntaxin 1a (or orthologs thereof).
synaptobrevin 2-SNAP-25-syntaxin-1a-complexin I complex A SNARE complex that contains synaptobrevin 2 (VAMP2), SNAP-25, syntaxin 1a, and complexin I (or orthologs thereof).
synaptobrevin 2-SNAP-25-syntaxin-1a-complexin II complex A SNARE complex that contains synaptobrevin 2 (VAMP2), SNAP-25, syntaxin 1a, and complexin II (or orthologs thereof).
synaptobrevin 2-SNAP-25-syntaxin-3-complexin complex A SNARE complex that contains synaptobrevin 2 (VAMP2), SNAP-25, syntaxin 3, and a complexin (or orthologs thereof).
syntrophin complex A protein complex that includes alpha-, beta1-, beta2-syntrophins and syntrophin-like proteins; the syntrophin complex binds to the second half of the carboxy-terminal domain of dystrophin; also associates with neuronal nitric oxide synthase.
T cell receptor complex A protein complex that contains a disulfide-linked heterodimer of T cell receptor (TCR) chains, which are members of the immunoglobulin superfamily, and mediates antigen recognition, ultimately resulting in T cell activation. The TCR heterodimer is associated with the CD3 complex, which consists of the nonpolymorphic polypeptides gamma, delta, epsilon, zeta, and, in some cases, eta (an RNA splice variant of zeta) or Fc epsilon chains.
TEAD-YAP complex
telomerase catalytic core complex The minimal catalytic core of telomerase is a ribonucleoprotein complex composed of a catalytic reverse transcriptase subunit and an RNA subunit that provides the template for telomeric DNA addition.
tenascin complex
terminal cisterna The portion of sarcoplasmic reticulum devoted to calcium ion storage and calcium ion release.
terminal web
tertiary granule A secretory granule that contains cathepsin and gelatinase and is readily exocytosed upon cell activation; found primarily in mature neutrophil cells.
tertiary granule lumen
tertiary granule membrane The lipid bilayer surrounding a tertiary granule.
THO complex part of transcription export complex The THO complex when it is part of the TREX (TRanscription EXport) complex that is involved in coupling transcription to export of mRNAs to the cytoplasm. In S. cerevisiae, it is composed of four subunits: Hpr1, Tho2, Thp1, and Mft1, while the human complex is composed of 7 subunits.
tight junction A cell-cell junction that seals cells together in an epithelium in a way that prevents even small molecules from leaking from one side of the sheet to the other.
TIM22 mitochondrial import inner membrane insertion complex A multi-subunit complex embedded in the mitochondrial inner membrane that mediates insertion of carrier proteins into the inner membrane.
TIM23 mitochondrial import inner membrane translocase complex The protein transport machinery of the mitochondrial inner membrane that contains three essential Tim proteins: Tim17 and Tim23 are thought to build a preprotein translocation channel while Tim44 interacts transiently with the matrix heat-shock protein Hsp70 to form an ATP-driven import motor.
Toll-like receptor 1-Toll-like receptor 2 protein complex A heterodimeric protein complex containing Toll-like receptor 1 (TLR1) and Toll-like receptor 2 (TLR2).
Toll-like receptor 2-Toll-like receptor 6 protein complex A heterodimeric protein complex containing Toll-like receptor 2 (TLR2) and Toll-like receptor 6 (TLR6).
TORC1 complex A protein complex that contains at least TOR (target of rapamycin) and Raptor (regulatory-associated protein of TOR), or orthologs of, in complex with other signaling components. Mediates the phosphorylation and activation of S6K. In Saccharomyces, the complex contains Kog1p, Lst8p, Tco89p, and either Tor1p or Tor2p.
TORC2 complex A protein complex that contains at least TOR (target of rapamycin) and Rictor (rapamycin-insensitive companion of TOR), or orthologs of, in complex with other signaling components. Mediates the phosphorylation and activation of PKB (also called AKT). In Saccharomyces, the complex contains Avo1p, Avo2p, Tsc11p, Lst8p, Bit61p, Slm1p, Slm2p, and Tor2p.
trans-Golgi network The network of interconnected tubular and cisternal structures located within the Golgi apparatus on the side distal to the endoplasmic reticulum, from which secretory vesicles emerge. The trans-Golgi network is important in the later stages of protein secretion where it is thought to play a key role in the sorting and targeting of secreted proteins to the correct destination.
trans-Golgi network membrane The lipid bilayer surrounding any of the compartments that make up the trans-Golgi network.
trans-Golgi network transport vesicle A vesicle that mediates transport between the trans-Golgi network and other parts of the cell.
trans-Golgi network transport vesicle membrane The lipid bilayer surrounding a vesicle transporting substances between the trans-Golgi network and other parts of the cell.
transcription factor AP-1 complex A heterodimeric transcription factor complex composed of proteins from the c-Fos, c-Jun, activating transcription factor (ATF) or JDP families. The subunits contain a basic leucine zipper (bZIP) domain that is essential for dimerization and DNA binding. Jun-Fos heterodimers bind preferentially to a heptamer consensus sequence (TPA responsive element (TRE)), whereas Jun-ATF dimers bind the cyclic AMP responsive element (CRE) to regulate transcription of target genes.
transcription factor TFIIA complex A component of the transcription machinery of RNA Polymerase II. In humans, TFIIA is a heterotrimer composed of an alpha (P35), beta (P19) and gamma subunits (P12).
transcription factor TFIID complex A complex composed of TATA binding protein (TBP) and TBP associated factors (TAFs); the total mass is typically about 800 kDa. Most of the TAFs are conserved across species. In TATA-containing promoters for RNA polymerase II (Pol II), TFIID is believed to recognize at least two distinct elements, the TATA element and a downstream promoter element. TFIID is also involved in recognition of TATA-less Pol II promoters. Binding of TFIID to DNA is necessary but not sufficient for transcription initiation from most RNA polymerase II promoters.
transcription factor TFIIE complex A transcription factor which in humans consists of a complex of two alpha and two beta chains. Recruits TFIIH to the initiation complex and helps activate both RNA polymerase II and TFIIH.
transcription factor TFIIF complex A general transcription initiation factor which in humans consists of a heterodimer of an alpha and a beta subunit. Helps recruit RNA polymerase II to the initiation complex and promotes translation elongation.
transcription factor TFIIH core complex The 7 subunit core of TFIIH that is a part of either the general transcription factor holo-TFIIH or the nucleotide-excision repair factor 3 complex. In S. cerevisiae/humans the complex is composed of: Ssl2/XPB, Tfb1/p62, Tfb2/p52, Ssl1/p44, Tfb4/p34, Tfb5/p8 and Rad3/XPD.
transcription factor TFIIH holo complex A complex that is capable of kinase activity directed towards the C-terminal Domain (CTD) of the largest subunit of RNA polymerase II and is essential for initiation at RNA polymerase II promoters in vitro. It is composed of the core TFIIH complex and the TFIIK complex.
transcription factor TFIIIB complex A transcription factor complex that is involved in regulating transcription from RNA polymerase III (Pol III) promoters. TFIIIB contains the TATA-binding protein (TBP) and two Pol III-specific proteins, B'' and BRF.
transcription factor TFIIIC complex A heterotrimeric transcription factor complex that is involved in regulating transcription from RNA polymerase III (Pol III) promoters. TFIIIC contains three conserved subunits that associate with the proximal Pol III promoter element, and additional subunits that associate with sequence elements downstream of the promoter and are more diverged among species. It also functions as a boundary element to partition genome content into distinct domains outside Pol III promoter regions.
transcription factor TFIIK complex A transcription factor complex that forms part of the holo TFIIH complex. In Saccharomyces/human, TFIIK contains Ccl1p/Cyclin H, Tfb3p/MAT1 and Kin2p/CDK7.
transcription factor TFTC complex A protein complex that does not contain either a TATA-binding protein (TBP) or a TBP-like factor, but is composed of several TAFIIs and other proteins, including a histone acetyltransferase. This complex is able to nucleate transcription initiation by RNA polymerase II, can mediate transcriptional activation, and has histone acetyltransferase activity.
transferase complex, transferring phosphorus-containing groups
transforming growth factor beta ligand-receptor complex A protein complex that is formed by the association of a ligand-bound TGF-beta type II receptor dimer with a TGF-beta type I receptor dimer.
transport vesicle membrane The lipid bilayer surrounding a transport vesicle.
TRAPPI protein complex
TRAPPII protein complex A complex that mediates intra-Golgi traffic, Golgi exit, endosome-to-Golgi traffic, and the trafficking of autophagy proteins from Golgi to the pre-autophagosomal structure. Binds to a component of the COPI coat. In yeast it includes the following subunits: Bet3 (as homodimer), Bet5, Tca17, Trs20, Trs23, Trs31, Trs33, Trs65, Tr120, Tr130. The whole complex is thought to dimerize with itself.
TRAPPIII protein complex A complex that functions in anterograde transport at the Golgi and also regulates autophagy. In yeast it includes at least the following subunits: Bet3 (as homodimer), Bet5, Trs20, Trs23, Trs31, Trs33, Trs85. TRAPPIII may include further, as yet undescribed, proteins.
tricellular tight junction
triglyceride-rich plasma lipoprotein particle A plasma lipoprotein particle that has a hydrophobic core enriched in triglycerides surrounded by an amphipathic monolayer of phospholipids, cholesterol and apolipoproteins. Triglyceride-rich lipoproteinparticles transport lipids, which are non-covalently associated with the particles, in the blood.
tRNA (m1A) methyltransferase complex A protein complex involved in the catalysis of the formation of the modified nucleotide 1-methyladenosine (m1A) in tRNA. In yeast, it is a heterotetramer of two subunits, Gcd10p and Gcd14p, while in bacteria and archaea it is a homotetramer.
tRNA (m7G46) methyltransferase complex
tRNA methyltransferase complex A multimeric protein complex involved in the methylation of specific nucleotides in tRNA.
type III intermediate filament A type of intermediate filament, typically made up of one or more of the proteins vimentin, desmin, glial fibrillary acidic protein (GFAP), and peripherin. Unlike the keratins, the type III proteins can form both homo- and heteropolymeric IF filaments.
U1 snRNP A ribonucleoprotein complex that contains small nuclear RNA U1.
U11/U12 snRNP A ribonucleoprotein complex formed by the association of the U11 and U12 small nuclear ribonucleoproteins.
U12-type spliceosomal complex Any spliceosomal complex that forms during the splicing of a messenger RNA primary transcript to excise an intron; the series of U12-type spliceosomal complexes is involved in the splicing of the majority of introns that contain atypical AT-AC terminal dinucleotides, as well as other non-canonical introns. The entire splice site signal, not just the terminal dinucleotides, is involved in determining which spliceosome utilizes the site.
U2 snRNP A ribonucleoprotein complex that contains small nuclear RNA U2.
U2-type catalytic step 1 spliceosome A spliceosomal complex that is formed by the displacement of the U1 and U4 snRNPs from the precatalytic spliceosome; the U2, U5 and U6 snRNPs remain associated with the mRNA. This complex, sometimes called the activated spliceosome, is the catalytically active form of the spliceosome, and includes many proteins in addition to those found in the U2, and U5 and U6 snRNPs.
U2-type catalytic step 2 spliceosome
U2-type post-mRNA release spliceosomal complex A spliceosomal complex that is formed following the release of the spliced product from the post-spliceosomal complex and contains the excised intron and the U2, U5 and U6 snRNPs.
U2-type post-spliceosomal complex
U2-type precatalytic spliceosome
U2-type prespliceosome A spliceosomal complex that is formed by association of the 5' splice site with the U1 snRNP, while the branch point sequence is recognized by the U2 snRNP. The prespliceosome includes many proteins in addition to those found in the U1 and U2 snRNPs. Commitment to a given pair of 5' and 3' splice sites occurs at the time of prespliceosome formation.
U2-type spliceosomal complex Any spliceosomal complex that forms during the splicing of a messenger RNA primary transcript to excise an intron that has canonical consensus sequences near the 5' and 3' ends.
U4 snRNP A ribonucleoprotein complex that contains small nuclear RNA U4.
U4/U6 snRNP A ribonucleoprotein complex that contains base-paired U4 and U6 small nuclear RNAs.
U4/U6 x U5 tri-snRNP complex A ribonucleoprotein complex formed by the association of the U4/U6 and U5 small nuclear ribonucleoproteins.
U4atac snRNP A ribonucleoprotein complex that contains small nuclear RNA U4atac.
U5 snRNP A ribonucleoprotein complex that contains small nuclear RNA U5.
U6 snRNP A ribonucleoprotein complex that contains small nuclear RNA U6.
U7 snRNP A ribonucleoprotein complex that contains the U7 snRNA and is required for the 3'-end processing of replication-dependent histone pre-mRNAs.
UBC13-MMS2 complex A heterodimeric ubiquitin conjugating enzyme complex that catalyzes assembly of K63-linked polyubiquitin chains, which act as a signal to promote error-free DNA postreplication repair; in Saccharomyces the complex comprises Ubc13p and Mms2p.
UBC13-UEV1A complex A heterodimeric ubiquitin conjugating enzyme complex that catalyzes assembly of K63-linked polyubiquitin chains and is involved in NF-kappaB activation. In humans at least, the complex comprises the ubiquitin-conjugating enzyme UBC13 and ubiquitin-conjugating enzyme variant 1A (UEV1A).
UDP-N-acetylglucosamine-lysosomal-enzyme N-acetylglucosaminephosphotransferase complex A protein complex that possesses UDP-N-acetylglucosamine-lysosomal-enzyme N-acetylglucosaminephosphotransferase activity; the bovine complex contains disulfide-linked homodimers of 166- and 51-kDa subunits and two identical, noncovalently associated 56-kDa subunits.
uniplex complex A calcium channel complex in the mitochondrial inner membrane capable of highly-selective calcium channel activity. Its components include the EF-hand-containing proteins mitochondrial calcium uptake 1 (MICU1) and MICU2, the pore-forming subunit mitochondrial calcium uniporter (MCU) and its paralog MCUb, and the MCU regulator EMRE.
vacuolar HOPS complex
vacuolar lumen The volume enclosed within the vacuolar membrane.
vacuolar membrane The lipid bilayer surrounding the vacuole and separating its contents from the cytoplasm of the cell.
vacuolar proton-transporting V-type ATPase complex A proton-transporting two-sector ATPase complex found in the vacuolar membrane, where it acts as a proton pump to mediate acidification of the vacuolar lumen.
vacuolar proton-transporting V-type ATPase, V0 domain The V0 domain of a proton-transporting V-type ATPase found in the vacuolar membrane.
vacuolar proton-transporting V-type ATPase, V1 domain The V1 domain of a proton-transporting V-type ATPase found in the vacuolar membrane.
VCB complex A protein complex that possesses ubiquitin ligase activity; the complex is usually pentameric; for example, in mammals the subunits are pVHL, elongin B, elongin C, cullin-2 (Cul2), and Rbx1.
very-low-density lipoprotein particle A triglyceride-rich lipoprotein particle that is typically composed of APOB100, APOE and APOCs and has a density of about 1.006 g/ml and a diameter of between 20-80 nm. It is found in blood and transports endogenous products (newly synthesized cholesterol and triglycerides) from the liver.
vesicle Any small, fluid-filled, spherical organelle enclosed by membrane or protein.
vesicle coat A membrane coat found on a coated vesicle.
vesicle lumen The volume enclosed by the membrane or protein that forms a vesicle.
vesicle membrane The lipid bilayer surrounding any membrane-bounded vesicle in the cell.
voltage-gated calcium channel complex A protein complex that forms a transmembrane channel through which calcium ions may pass in response to changes in membrane potential.
voltage-gated potassium channel complex A protein complex that forms a transmembrane channel through which potassium ions may cross a cell membrane in response to changes in membrane potential.
voltage-gated sodium channel complex A sodium channel in a cell membrane whose opening is governed by the membrane potential.
Weibel-Palade body A large, elongated, rod-shaped secretory granule characteristic of vascular endothelial cells that contain a number of structurally and functionally distinct proteins, of which the best characterized are von Willebrand factor (VWF) and P-selectin. Weibel-Palade bodies are formed from the trans-Golgi network in a process that depends on VWF, which is densely packed in a highly organized manner, and on coat proteins that remain associated with the granules. Upon cell stimulation, regulated exocytosis releases the contained proteins to the cell surface, where they act in the recruitment of platelets and leukocytes and in inflammatory and vasoactive responses.
WICH complex An ISWI complex that contains an ATPase subunit of the ISWI family (specifically SNF2H in mammals, which contain two ISWI homologs) and WSTF (Williams Syndrome Transcription Factor). WICH plays roles in regulation of RNAP I and III transcription and in DNA replication and repair.
Wnt-Frizzled-LRP5/6 complex
X chromosome The sex chromosome present in both sexes of species in which the male is the heterogametic sex. Two copies of the X chromosome are present in each somatic cell of females and one copy is present in males.
XPC complex A nucleotide-excision repair complex that is involved in damage sensing during global genome nucleotide excision repair (GG-NER). It is part of the pre-incision (or initial recognition) complex bound to sites of DNA damage. In human, it is composed of XPC, RAD23B and CETN2.
zeta DNA polymerase complex A heterodimeric DNA polymerase complex that catalyzes error-prone DNA synthesis in contexts such as translesion synthesis and double-stranded break repair. First characterized in Saccharomyces, in which the subunits are Rev3p and Rev7p; a third protein, Rev1p, is often associated with the polymerase dimer.
zonula adherens A cell-cell adherens junction which forms a continuous belt near the apex of epithelial cells.
zymogen granule A membrane-bounded, cytoplasmic secretory granule found in enzyme-secreting cells and visible by light microscopy. Contain zymogen, an inactive enzyme precursor, often of a digestive enzyme.
zymogen granule membrane The lipid bilayer surrounding a zymogen granule.