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. Protein modification; protein glycosylation. Component of the oligosaccharyltransferase (OST) complex. Widely expressed. Greatest expression seen in the epidermis, intermediate expression in the fat body and midgut and mild expression observed in the silk gland. Expression is significantly induced at 4 degrees Celsius and at 37 degrees Celsius compared to the control which was maintained at 25 degrees Celsius. There is a dramatic increase every 5 hours of each temperature treatment suggesting that over-expression is a cell response to inhibit programmed cell death by external temperature stimulus. Belongs to the DAD/OST2 family.