ID:STT3B_HUMAN DESCRIPTION: RecName: Full=Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit STT3B; Short=Oligosaccharyl transferase subunit STT3B; Short=STT3-B; EC=2.4.1.119; AltName: Full=Source of immunodominant MHC-associated peptides homolog; FUNCTION: Catalytic component of oligosaccharyltransferase (OST) 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. Mediates glycosylation of the disease variant AMYL-TTR 'Asp-38' of TTR at 'Asn-118', leading to its degradation. CATALYTIC ACTIVITY: Dolichyl diphosphooligosaccharide + protein L- asparagine = dolichyl diphosphate + a glycoprotein with the oligosaccharide chain attached by N-glycosyl linkage to protein L- asparagine. SUBUNIT: Component of the oligosaccharyltransferase (OST) complex (By similarity). 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. SUBCELLULAR LOCATION: Endoplasmic reticulum membrane; Multi-pass membrane protein. TISSUE SPECIFICITY: Expressed in heart, brain, placenta, lung, liver, muscle, kidney and pancreas. Expressed in skin fibroblasts (at protein level). SIMILARITY: Belongs to the STT3 family. SEQUENCE CAUTION: Sequence=AAH15880.1; Type=Erroneous initiation; Note=Translation N-terminally extended; Sequence=BAB55370.1; Type=Erroneous initiation; Note=Translation N-terminally extended; Sequence=BAC11581.1; Type=Erroneous initiation; Note=Translation N-terminally extended;
The RNAfold program from the Vienna RNA Package is used to perform the secondary structure predictions and folding calculations. The estimated folding energy is in kcal/mol. The more negative the energy, the more secondary structure the RNA is likely to have.
ModBase Predicted Comparative 3D Structure on Q8TCJ2
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Orthologous Genes in Other Species
Orthologies between human, mouse, and rat are computed by taking the best BLASTP hit, and filtering out non-syntenic hits. For more distant species reciprocal-best BLASTP hits are used. Note that the absence of an ortholog in the table below may reflect incomplete annotations in the other species rather than a true absence of the orthologous gene.
Gene Ontology (GO) Annotations with Structured Vocabulary
Molecular Function: GO:0004576 oligosaccharyl transferase activity GO:0004579 dolichyl-diphosphooligosaccharide-protein glycotransferase activity GO:0016740 transferase activity GO:0016757 transferase activity, transferring glycosyl groups GO:0046872 metal ion binding
Biological Process: GO:0006486 protein glycosylation GO:0006516 glycoprotein catabolic process GO:0006986 response to unfolded protein GO:0018279 protein N-linked glycosylation via asparagine GO:0030433 ER-associated ubiquitin-dependent protein catabolic process GO:0043686 co-translational protein modification GO:0043687 post-translational protein modification
Cellular Component: GO:0005783 endoplasmic reticulum GO:0005789 endoplasmic reticulum membrane GO:0008250 oligosaccharyltransferase complex GO:0016020 membrane GO:0016021 integral component of membrane
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Sequence and Links to Tools and Databases 
Common Gene Haplotype Alleles 
