Structural studies on H-2D b and H-2K d molecules indicate that murine major histocompatibility b and d haplotype alloantigens share structural features

Abstract

Structural properties of the H-2D b and H-2K d murine major histocompatibility complex (MHC) antigens were examined by radiochemical methods. Radiolabelled preparations of the H-2D b and H-2K d antigens were obtained by indirect immune precipitation of NP-40 lysates of the lymphoid tumor cell lines EL-4 (H-2 b) and C14 (H-2 d), respectively. After preparation of the 37,000 molecular weight papain fragment the antigens were cleaved with CNBr. The H-2K d antigen yielded four major CNBr fragments whereas the H-2D b molecule provided six. These CNBr fragments were subjected to partial NH 2-terminal amino acid sequence analysis and aligned by homology to the H-2K b glycoprotein. Comparison of the structural properties of the H-2K d and H-2D b molecules with previously published data on the other known major transplantation antigens of the b and d haplotypes (H-2K b, H-2D d and H-2L d) reveal a marked structural similarity. First, the data show that certain methionine residues have been highly conserved and that cleavage by CNBr at these positions provides an initial strategy for the study of these molecules. Secondly, disulfide-linked peptides obtained after CNBr cleavage could be aligned and the data suggest the presence of disulfide bridges in homologous positions. Third, after CNBr cleavage both the H-2K d and H-2D b molecules yielded two glycopeptides which were homologous to glycopeptides from the H-2K b molecule. Fourth, overall homology for a limited number of comparable positions is about 81% between the H-2K b and H-2K d gene products and 88% between the H-2K b and H-2D b gene products.