Oligosaccharyltransferase (OST) catalyzes the central step in N-linked protein glycosylation, transfer of a preassembled oligosaccharide from its lipid carrier onto asparagine residues secretory proteins. The prototypic hetero-octameric OST complex yeast Saccharomyces cerevisiae exists as two isoforms that contain either Ost3p or Ost6p, both noncatalytic subunits. These complexes have different...
