COMPARISON OF THE N-LINKED OLIGOSACCHARIDE STRUCTURES OF THE 2 MAJOR HUMAN MYELIN GLYCOPROTEINS MAG AND P0 - ASSESSMENT AND RELATIVE OCCURRENCE OF OLIGOSACCHARIDE STRUCTURES BY SERIAL LECTIN AFFINITY-CHROMATOGRAPHY OF C-14 GLYCOPEPTIDES

The N-linked oligosaccharide structures of human myelin-associated glycoprotein (MAG) and P0 have been characterized by serial lectin affinity chromatography (SLAC) of C-14-glycopeptides. C-14-Glycopeptides were prepared from purified MAG derivative and P0 by extensive proteolytic digestion and N-C-14-acetylation. Assuming that all the C-14-glycopeptides were radiolabelled to the same specific radioactivity, the relative occurrence of the oligosaccharide structures was correlated to the amount of incorporated radioactivity. Sixteen and 15 fractions were generated by SLAC of MAG and P0 C-14-glycopeptides, respectively. Despite this tremendous structural heterogeneity, the oligosaccharide "fingerprints" of MAG and P0 obtained by SLAC displayed similarities: (a) of the three types of N-linked oligosaccharides, the complex type accounted for 80.4% and 94.9% of MAG and P0 radioactivity, respectively; (b) biantennary complex oligosaccharides were the major structures present on MAG and P0; (c) almost-equal-to 60% of MAG and P0 oligosaccharides possessed a bisecting N-acetylglucosamine residue; and (d) large amounts of oligosaccharides with an alpha(1-6)fucose residue were found in both MAG and P0 and, noticeably, almost-equal-to 25% of the tri- and/or tetraantennary and almost-equal-to 90% of the bisected biantennary oligosaccharides of both glycoproteins contained alpha(1-6)fucose residues in the core. This study demonstrates that MAG and P0, both belonging to the immunoglobulin superfamily, display structural similarities in their N-linked oligosaccharide contents.