The function of ENSG00000198856 (OSTC, oligosaccharyltransferase complex non-catalytic subunit) is as follows. Subunit of STT3A-containing oligosaccharyl transferase (OST- A) 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 (PubMed:28860277, PubMed:31831667, PubMed:39509507). 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) (PubMed:28860277, PubMed:31831667, PubMed:39509507). Within the OST-A complex, acts as an adapter that anchors the OST-A complex to the Sec61 complex (PubMed:28860277). May be involved in N-glycosylation of APP (amyloid-beta precursor protein) (PubMed:21768116). Can modulate gamma-secretase cleavage of APP by enhancing endoprotelysis of PSEN1 (PubMed:21768116). {ECO:0000269|PubMed:21768116, ECO:0000269|PubMed:28860277, ECO:0000269|PubMed:31831667, ECO:0000269|PubMed:39509507}.