The oligosaccharyltransferase complex is a multi-span membrane protein complex that catalyzes the addition of glycans to selected Asn residues within nascent polypeptides in the lumen of the endoplasmic reticulum. This process, termed N-glycosylation, is a fundamental post-translational protein modification involved in quality control, trafficking of proteins, signal transduction, and cell-to-cell communication. Mammalian cells express two distinct OST complexes that contain STT3A or STT3B as the catalytic subunit and several accessory proteins: six common subunits, two STT3A-OST-specific subunits and two STT3B-OST-specific subunits. The two OST complexes are known to have distinct, but partially overlapping roles. (Adapted from
PMID:31810196.)
