Beschreibung:
<jats:p>
<jats:italic>N</jats:italic>‐Oligosaccharyltransferase catalyzes the <jats:italic>N</jats:italic>‐glycosylation of asparagine residues of nascent polypeptide chains in the endoplasmic reticulum, a pathway highly conserved in all eukaryotes. An enzymatically active complex was isolated from microsomal membranes from <jats:italic>Saccharomyces cerevisiae</jats:italic>, which is composed of four proteins: Wbplp and Swplp (previously found to be encoded by two essential genes necessary for N‐glycosylation in vivo and in vitro) and two additional proteins with a molecular mass of 60/62 kDa and 34 kDa. The 60/62 component represents differentially glycosylated forms of a protein that has sequence homology to ribophorin I. Wbplp and Swplp reveal homology to mammalian OST 48 and ribophorin II, respectively. Ribophorin I and II and OST 48 were recently shown to be constituents of the mammalian transferase from dog pancreas. The data reveal a high conservation of the organization of this enzyme activity.</jats:p>