chart adapted from:Bill, et. al., Protein Glycosylation (283)
click a core diagram to view it in 3D
O-Glycan information
Protein glycosylation at serine or threonine residues by GalNAc results in an O-linked GalNAc residue.
The biosynthesis of O-glycans differs from that of N-linked glycans in that the latter requires a lipid-linked
core precursor, while the former does not, and that a consensus sequence for GalNAc addition has not
been estimated Synthesis begins upon the addition of GalNAc (donated by UDP-GalNAc) by GalNAc transferases
to Ser/Thr catalyzed by a GalNAc transferase.
O-glycans are less branched than most N-glycans, and are commonly found in biantennary structures. O-glycans
may be found clustered on cell surface or secreted glycoproteins, called mucins.
Ser/Thr glycosylation occurs in the secretory pathway of all eukaryotic cells, O-glycosylation refers
to a GalNac residue a-linked to the hydroxyl group of Ser/Thr residues.
O-glycosylation requires the action of a family of polypeptide GalNAc transferases. The GalNAcTs are
similar to other glycosyltransferases in that they are type II transmembrane poteins. It has been
suggested that at least eight GalNAcTs exist in humans and that they are relatively homologous to each other.
Site designed and maintained by Aidan Ryan, LECB Structural Glycobiology Section, NCI Frederick, Maryland
