Microheterogeneity and oligosaccharide chains on the beta chains of HLA-DR, human major histocompatibility complex...

The beta chain of human histocompatibility complex class II antigen, HLA-DR, showed 4 to 5 microheterogeneous spots on a gel obtained by two-dimensional polyacrylamide gel electrophoresis. The types of oligosaccharide chains on the beta chains were analyzed by the lectin-nitrocellulose sheet method for each microheterogeneous spot with 3 cell lines of two haplotypes (HLA-DR 4,4, and 3,3). Two kinds of oligosaccharide chains were observed and were essentially the same in the microheterogeneous spots from all three cell lines. One, the oligosaccharide chain on the most basic spot (beta 1), was stained with peroxidase-coupled concanavalin A (Con A-P.O.) but not with peroxidase-coupled wheat germ agglutinin and was sensitive to endo-beta-N-acetylglucosaminidase H (endo H), indicating that it was a high-mannose type. The oligosaccharide chains on other spots that were not stained with Con A-P.O. but were stained with peroxidase-coupled Ricinus communis agglutinin were resistant to endo H. beta 2 and beta 3 were stained with E-PHA. Thus, they probably had bisected biantennary and others probably had multiantennary complex-type oligosaccharides. Sialidase experiments showed that the charge heterogeneity was due to post-translational sialylation of the oligosaccharide chains. In pulse-chase experiments, the most basic spot of beta chain (beta 1) was labeled first, beta 2 and beta 3 were labeled next, and beta 4 was labeled last. These labeling characters accorded well with the results on the oligosaccharide types mentioned above.