Structural characterization of murine Ia antigen N-linked oligosaccharides and localization of specific structures to two unique alpha-chain glycosylation sites.
The sequence of N-linked oligosaccharides of differentially glycosylated murine I-Ak alpha-(alpha 2- and alpha 3-) and beta-chains was determined. I-Ak beta-chains predominantly bear a biantennary complex oligosaccharide with a core fucose, and with the peripheral sequence SA----Gal----GlcNAc----Man. The I-Ak alpha-chain has two N-linked glycosylation sites at Asn-82 and Asn-122. When Lubrol-insoluble alpha 3-chains are examined they are found to bear high-mannose oligosaccharides of either the Man9GlcNAc2 or Man8GlcNAc2 type at both sites. When Lubrol-soluble alpha 2-chains are examined, in about 85% of the molecules the Asn-82 site bears a biantennary complex oligosaccharide with core fucose, and with the peripheral sequence SA----Gal----GlcNAc----Man. Interestingly, the Asn-122 site bears a variety of structures. In about 50% of the molecules, the structure at Asn-122 is a biantennary complex oligosaccharide without core fucose and with the peripheral sequence SA----Gal----GlcNAc----Man. In addition, it can bear other complex structures which we did not define further. The apparently restricted addition of fucose to the oligosaccharide at the alpha-Asn-82 site, even when both alpha-sites bear biantennary complex structures with the same peripheral sequence, is a feature unique to this system. The unusual variety of structures present at the alpha-Asn-122 site may indicate differential processing in different cell types.
D000818:Animals; D002240:Carbohydrate Sequence; D055598:Chemical Phenomena; D002621:Chemistry; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006020:Glycopeptides / Q000302:isolation & purification; D000949:Histocompatibility Antigens Class II; D008358:Mannose / Q000032:analysis; D051379:Mice; D008815:Mice, Inbred Strains; D009844:Oligosaccharides / Q000032:analysis*
D006020:Glycopeptides; D000949:Histocompatibility Antigens Class II; D009844:Oligosaccharides; D008358:Mannose