ABSTRACT
Protein glycosylation: overview Most proteins made by ribosomes on the RER (Section H4) are glycoproteins, that is they contain short chains of carbohydrates (oligosaccharides) covalently linked to them during passage through the RER and Golgi complex. Two main types of oligosaccharide linkage exist:
z O-linked oligosaccharides are commonly attached to the protein via O-glycosidic bonds to OH groups of Ser or Thr side chains (Figure 1a). The residues that are modified are often in a region of the polypeptide chain that is rich in Ser and/or Thr residues. In plant glycoproteins, the OH groups of hydroxyproline (Hyp) residues can be glycosylated, while the hydroxylysine (Hyl) residues in the mammalian protein collagen can be O-glycosylated (Section B4).
