{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Hemoglobin is a multifaceted protein that serves as the central oxygen‐carrier in erythrocytes while also playing key roles in iron metabolism and cellular redox regulation. Its classic function in oxygen transport is intricately linked to its ability to bind, deliver, and release oxygen in a controlled manner—a process that depends on finely tuned ligand‐binding kinetics, allosteric transitions, and subunit interactions."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": " \n In addition to its oxygen transport role, hemoglobin is central to maintaining cellular iron homeostasis and modulating oxidative stress, as evidenced by its participation in multiprotein complexes required for proper heme biosynthesis and repair of iron‐sulfur cluster deficiencies."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Hemoglobin function is further regulated at the level of erythroid progenitor expansion and differentiation, where signaling through receptor pathways can induce robust erythropoiesis independent of extracellular cues"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": ", and by transcription factors such as GATA‐1, which coordinate the expression of hemoglobin subunits and associated heme biosynthetic enzymes."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": " Moreover, strategies to enhance the stability and assembly of recombinant hemoglobin have shown promise in the development of oxygen therapeutics."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In addition to its well‐established role in red blood cells, hemoglobin (or its subunits) is expressed in non‐canonical, avascular tissues such as the lens and in early embryos, suggesting additional, context‐dependent functions that may extend beyond oxygen delivery."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": " Genetic and structural studies have also illuminated the clinical impact of hemoglobin variants; abnormal hemoglobin forms are responsible for a range of hemoglobinopathies whose epidemiology and molecular pathology have been extensively characterized."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Finally, investigations into the quaternary structure of hemoglobin—from the classical tetrameric assembly to the massive extracellular complexes found in invertebrates—reveal an evolutionary diversity that underscores the protein’s adaptability. These studies show that subtle modifications (including N‐terminal changes) and variable oligomerization can modulate both ligand binding and allosteric responses."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}, {"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": "\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Michael John Kerins, Aikseng Ooi "}, {"type": "b", "children": [{"type": "t", "text": "The Roles of NRF2 in Modulating Cellular Iron Homeostasis."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Antioxid Redox Signal (2018)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1089/ars.2017.7176"}], "href": "https://doi.org/10.1089/ars.2017.7176"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "28793787"}], "href": "https://pubmed.ncbi.nlm.nih.gov/28793787"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Raymond M Esquerra, Ignacio López-Peña, Pooncharas Tipgunlakant, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Kinetic spectroscopy of heme hydration and ligand binding in myoglobin and isolated hemoglobin chains: an optical window into heme pocket water dynamics."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Phys Chem Chem Phys (2010)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1039/c003606b"}], "href": "https://doi.org/10.1039/c003606b"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "20668762"}], "href": "https://pubmed.ncbi.nlm.nih.gov/20668762"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Makoto Ashiuchi, Takeshi Yagami, Ronald J Willey, et al. "}, {"type": "b", "children": [{"type": "t", "text": "N-terminal acetylation and protonation of individual hemoglobin subunits: position-dependent effects on tetramer strength and cooperativity."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Protein Sci (2005)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1110/ps.041267405"}], "href": "https://doi.org/10.1110/ps.041267405"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "15929996"}], "href": "https://pubmed.ncbi.nlm.nih.gov/15929996"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Nunziata Maio, Ki Soon Kim, Gregory Holmes-Hampton, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Dimeric ferrochelatase bridges ABCB7 and ABCB10 homodimers in an architecturally defined molecular complex required for heme biosynthesis."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Haematologica (2019)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.3324/haematol.2018.214320"}], "href": "https://doi.org/10.3324/haematol.2018.214320"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "30765471"}], "href": "https://pubmed.ncbi.nlm.nih.gov/30765471"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Chintan Parekh, Arineh Sahaghian, William Kim, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Novel pathways to erythropoiesis induced by dimerization of intracellular C-Mpl in human hematopoietic progenitors."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Stem Cells (2012)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1002/stem.1046"}], "href": "https://doi.org/10.1002/stem.1046"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "22290824"}], "href": "https://pubmed.ncbi.nlm.nih.gov/22290824"}]}, {"type": "r", "ref": 6, "children": [{"type": "t", "text": "Koichi R Katsumura, Andrew W DeVilbiss, Nathaniel J Pope, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Transcriptional mechanisms underlying hemoglobin synthesis."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Cold Spring Harb Perspect Med (2013)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1101/cshperspect.a015412"}], "href": "https://doi.org/10.1101/cshperspect.a015412"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "23838521"}], "href": "https://pubmed.ncbi.nlm.nih.gov/23838521"}]}, {"type": "r", "ref": 7, "children": [{"type": "t", "text": "Philip E Graves, Douglas P Henderson, Molly J Horstman, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Enhancing stability and expression of recombinant human hemoglobin in E. coli: Progress in the development of a recombinant HBOC source."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Biochim Biophys Acta (2008)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.bbapap.2008.04.012"}], "href": "https://doi.org/10.1016/j.bbapap.2008.04.012"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "18489914"}], "href": "https://pubmed.ncbi.nlm.nih.gov/18489914"}]}, {"type": "r", "ref": 8, "children": [{"type": "t", "text": "Fiona C Mansergh, Susan M Hunter, Jenny C Geatrell, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Developmentally regulated expression of hemoglobin subunits in avascular tissues."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Int J Dev Biol (2008)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1387/ijdb.082597fm"}], "href": "https://doi.org/10.1387/ijdb.082597fm"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "18956317"}], "href": "https://pubmed.ncbi.nlm.nih.gov/18956317"}]}, {"type": "r", "ref": 9, "children": [{"type": "t", "text": "M Lin, Q Wang, L Zheng, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Prevalence and molecular characterization of abnormal hemoglobin in eastern Guangdong of southern China."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Clin Genet (2012)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1111/j.1399-0004.2011.01627.x"}], "href": "https://doi.org/10.1111/j.1399-0004.2011.01627.x"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "21231928"}], "href": "https://pubmed.ncbi.nlm.nih.gov/21231928"}]}, {"type": "r", "ref": 10, "children": [{"type": "t", "text": "Tobias Lamkemeyer, Bettina Zeis, Heinz Decker, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Molecular mass of macromolecules and subunits and the quaternary structure of hemoglobin from the microcrustacean Daphnia magna."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "FEBS J (2006)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1111/j.1742-4658.2006.05346.x"}], "href": "https://doi.org/10.1111/j.1742-4658.2006.05346.x"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "16857019"}], "href": "https://pubmed.ncbi.nlm.nih.gov/16857019"}]}]}]}