Other Classes of Eukaryotic Glycans

Excerpt

This chapter focuses on several less easily categorized types of glycoprotein linkages that occur on specific proteins or domains, most of which have specific biological functions. O-linked modifications of epidermal growth factor (EGF)-like repeats (O-fucose, O-glucose, and O-GlcNAc) regulate the Notch signaling pathway. O-Fucosylation of thrombospondin type 1 repeats (TSRs) is required for folding of these domains in a number of secreted matricellular proteins. O-Mannosylation of α-dystroglycan is essential for interactions with several extracellular matrix proteins. Defects in the glycosyltransferases that add these glycans (O-fucose, O-glucose, O-GlcNAc, and O-mannose) result in human diseases. C-Mannosylation is a unique form of glycosylation in which mannose is linked through a carbon–carbon bond to tryptophan. O-Linked galactose disaccharides are added to hydroxyproline and hydroxylysine residues and play an important role in collagen fibril formation. Although the glycans described here are found on relatively few glycoproteins, they play specific and important roles in biology.