N-oligosaccharyl transferase (OST)

Function

• catalyzes transfer of a high mannose oligosaccharide from a dolichol-linked oligosaccharide donor to an Asn within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains
• N-glycosylation occurs cotranslational
• associates with the Sec61 complex at the channel-forming translocon complex that mediates protein translocation across the endoplasmic reticulum

Structure

• consists of:
  • RPN1, RPN2, OST48, DAD1, & either STT3A or STT3B
• OST4 may also be associated

Compartment

endoplasmic reticulum membrane

Expression

• expressed in placenta, liver, muscle, pancreas > brain, lung & kidney
• expressed in skin fibroblasts

More general terms

• glycosyltransferase
• molecular complex