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). In addition may regulates nuclear envelope (NE) architecture and nuclear positioning through the linker of nucleoskeleton and cytoskeleton (LINC)-dependent and -independent mechanisms (PubMed:28716842). Homodimer (PubMed:28716842). Component of the oligosaccharyltransferase (OST) complex (By similarity). Interacts with klar and Msp300, components of LINC complex (PubMed:28716842). Homozygous mutants display growth retardation and dy as larvae and show defects in ovarian follicle cells, which enwrap the germ cell clusters in ovarioles. Belongs to the OST5 family.