Figure 1.

Illustration of the N- and O-link glycosylation, and O-GlcNAcylation. The structures and locations of the canonical N- and O-link glycosylation are compared to those of the non-canonical, cancer-specific O-GlcNAcylation. The N-link glycosylation involves complex combinations of mannose, galactose, and GlcNAc, with a common core composed of 2 GlcNAcs and 3 mannoses. The O-link glycosylation is initiated by the addition of a GalNAc group, and the sugar chains are extended by sequential addition of galactose, GalNAc and GlcNAc. N- and O-link glycosylation are often capped with negatively charged sialic acids. The O-GlcNAcylation is initiated by a GlcNAc, and can be further extended by addition of galactose and sialic acid. Note the intracellular as well as membrane location of O-GlcNAcylation.

Abbreviations: GlcNAc, N-acetylglucosamine; Man, mannose; Gal, galactose; GalNAc, N-acetylgalactosamine; SA, sialic acid; Fuc, fucose.