Tumor suppressor candidate 3 (TUSC3)

Acts as accessory component 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. Involved in N-glycosylation of STT3B-dependent substrates.

Specifically necessary for the glycosylation of a subset of acceptor sites that are close cysteine residues; in this event appears to act redundantly with MAGT1. In its oxidized form suggested to form transient mixed disulfides with a glycoprotein substrate to ease access to STT3B to the unmodified acceptor site.