Ost1 Background Information Membrane proteins of the endoplasmic reticulum (ER) may be localized by mechanisms that involve retention, retrieval, or a combination of both. ER localization information has been found in cytoplasmic, transmembrane, or luminal domains. Specific retrieval mechanisms have been identified for luminal ER proteins, which contain a KDEL domain, and for type I transmembrane proteins carrying a dilysine motif. Oligosaccharyl transferase alpha subunit (Ost1) (also designated Dolichyl-diphosphooligosaccharide protein glycosyltransferase alpha subunit) is a protein belonging to the ribophorin I family of proteins. In polypeptide chains, Ost1 catalyzes the transfer of high mannose oligosaccharide to an asparagine residue within an Asn-X-Ser/Thr consensus motif.
