Human dolichyl-diphosphooligosaccharide-protein glycosyltransferase,DDOST;OST-48

Essential subunit of the N-oligosaccharyl transferase (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.

Required for the assembly of both SST3A- and SS3B-containing OST complexes.

Required for efficient N-glycosylation.

{ECO:0000250|UniProtKB:Q05052, ECO:0000269|PubMed:22467853, ECO:0000305}.; 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 (By similarity).

Required for the assembly of both SST3A- and SS3B-containing OST complexes (PubMed:22467853).

{ECO:0000250|UniProtKB:Q05052, ECO:0000269|PubMed:22467853}.