title: Chemical cross-linking of Ia alloantigen alpha and beta chains with dimethyl 3,3'-dithiobispropionimidate.
abstract: We have examined the polypeptide chain composition of membrane-bound and detergent-solubilized Ia antigens using the chemical cross-linking reagent dimethyl 3,3'-dithiobispropionimidate (DTBP). Products of the I-E/C subregion of the major histocompatibility complex, which were solubilized from spleen cells with the detergent NP-40 and partially purified by affinity chromatography on lentil lectin-agarose, could be almost completely cross-linked by DTBP. Thus, the characteristic 33,000 m.v. (alpha) and 28,000 (beta) polypeptide chains seen on sodium dodecylsulfate polyacrylamide gels disappeared and a major new species of 60,000 m.w. appeared after cross-linking. When isolated and reduced with 2-mercaptoethanol, the 60,000 m.w. peak was found to be comprised to alpha and beta chains. Similar results were obtained when I-E/C, as well as I-A, alpha and beta chains were crosslinked on the cell surface. These data demonstrate that the alpha and beta chains of the Ia antigens exist primarily in the form of a dimer both in detergent solution and in situ.
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000276:immunology; D003429:Cross Reactions; D003902:Detergents / Q000494:pharmacology; D004220:Disulfides / Q000494:pharmacology; D006649:Histocompatibility Antigens / Q000276:immunology*; D007094:Imides / Q000494:pharmacology*; D007096:Imidoesters; D007202:Indicators and Reagents / Q000494:pharmacology; D051379:Mice; D008970:Molecular Weight; D010455:Peptides / Q000276:immunology; D012995:Solubility
chemical_list: D000954:Antigens, Surface; D003902:Detergents; D004220:Disulfides; D006649:Histocompatibility Antigens; D007094:Imides; D007096:Imidoesters; D007202:Indicators and Reagents; D010455:Peptides; C007471:dimethyl dithiobispropionimidate