{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nThe human tRNA‐guanine transglycosylase (TGT) enzyme operates as a heterodimer composed of two distinct subunits. In the studies summarized here"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": ", one subunit—QTRT1—has been identified as the catalytic component responsible for the transglycosylation of tRNA substrates, while the second component, previously named QTRTD1, appears necessary for activity. Although initially there was a suggestion that USP14 might be a regulatory subunit, the data clearly show that the enzyme’s activity is only observed when QTRT1 is co‐expressed and co‐purified with QTRTD1. \n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nInterestingly, emerging work proposes that what is here referred to as QTRTD1 (and which may also be designated as QTRT2 in some literature) functions as a “salvage” enzyme. It is hypothesized to generate free queuine from queuine monophosphate (QMP), thereby providing the queuine moiety that is ultimately incorporated into specific tRNAs. The kinetic characterization of the TGT heterodimer in human cells mirrors the efficiency observed for the eubacterial enzyme, further underscoring the functional conservation of this modification system."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nThus, the summarized function of QTRT2 (alias QTRTD1) is twofold: it is essential for enabling the enzymatic transglycosylation activity of QTRT1 by forming a functional heterodimer, and it may also serve as a salvage enzyme that recycles queuine from QMP, ensuring the proper modification of tRNA necessary for efficient cellular translation.\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Yi-Chen Chen, Vincent P Kelly, Stefanie V Stachura, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Characterization of the human tRNA-guanine transglycosylase: confirmation of the heterodimeric subunit structure."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "RNA (2010)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1261/rna.1997610"}], "href": "https://doi.org/10.1261/rna.1997610"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "20354154"}], "href": "https://pubmed.ncbi.nlm.nih.gov/20354154"}]}]}]}