STT3, Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit STT3
Enzyme Classification 188.8.131.52
Also Known as
Catalytic subunit of the oligosaccharyl transferase (OST) complex that catalyzes the initial transfer of a defined glycan (Glc(3)Man(9)GlcNAc(2) in eukaryotes) from the lipid carrier dolichol-pyrophosphate to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains, the first step in protein N-glycosylation. N-glycosylation occurs cotranslationally and the complex associates with the Sec61 complex at the channel-forming translocon complex that mediates protein translocation across the endoplasmic reticulum (ER). All subunits are required for a maximal enzyme activity (PubMed:12359722). This subunit contains the active site and the acceptor peptide and donor lipid-linked oligosaccharide (LLO) binding pockets (PubMed:29301962). Component of the oligosaccharyltransferase (OST) complex, which appears to exist in two assemblies comprising OST1, OST2, OST4, OST5, STT3, SWP1, WPB1, and either OST3 or OST6 (PubMed:10677492, PubMed:16297388, PubMed:16096345, PubMed:15831493, PubMed:15886282, PubMed:9405463, PubMed:9435788, PubMed:29301962). OST assembly occurs through the formation of 3 subcomplexes. Subcomplex 1 contains OST1 and OST5, subcomplex 2 contains STT3, OST3, and OST4, and subcomplex 3 contains OST2, WBP1, and SWP1 (PubMed:29301962). Interacts with SEC61 (PubMed:15831493).