LMPD Database

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LMP004846

UniProt Annotations

Entry Information
Gene NameSTT3, subunit of the oligosaccharyltransferase complex, homolog B (S. cerevisiae)
Protein EntrySTT3B_MOUSE
UniProt IDQ3TDQ1
SpeciesMouse
Comments
Comment typeDescription
Catalytic ActivityDolichyl diphosphooligosaccharide + [protein]- L-asparagine = dolichyl diphosphate + a glycoprotein with the oligosaccharide chain attached by N-beta-D-glycosyl linkage to a protein L-asparagine.
FunctionCatalytic component of oligosaccharyltransferase (OST) complex which catalyzes the transfer of a high mannose oligosaccharide from a lipid-linked oligosaccharide donor to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains. 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). STT3B is present in a small subset of OST complexes and mediates both cotranslational and post-translational N-glycosylation of target proteins: STT3B-containing complexes are required for efficient cotranslational glycosylation and while they are less competent than STT3A-containing complexes for cotranslational glycosylation, they have the ability to mediate glycosylation of some nascent sites that are not accessible for STT3A. STT3B-containing complexes also act post-translationally and mediate modification of skipped glycosylation sites in unfolded proteins. Plays a role in ER-associated degradation (ERAD) pathway that mediates ubiquitin-dependent degradation of misfolded endoplasmic reticulum proteins by mediating N-glycosylation of unfolded proteins, which are then recognized by the ERAD pathway and targeted for degradation (By similarity). {ECO:0000250}.
PolymorphismIn strains 129, C57BL/10, C57BL/6 and LP Glu-776 correlates with a B6dom1-positive phenotype, Asp-776 is found in resistant strains. The B6dom1 minor histocompatibilty antigen (MiHA) is used as a model antigen in studying immunodominance.
Sequence CautionSequence=AAH13054.2; Type=Erroneous initiation; Evidence={ECO:0000305};
Subcellular LocationEndoplasmic reticulum membrane; Multi-pass membrane protein.
SubunitComponent of the oligosaccharyltransferase (OST) complex. OST seems to exist in different forms which contain at least RPN1, RPN2, OST48, DAD1, OSTC, KRTCAP2 and either STT3A or STT3B. OST can form stable complexes with the Sec61 complex or with both the Sec61 and TRAP complexes (By similarity). {ECO:0000250}.