Intramolecular organization of Class I H-2 MHC antigens; localization of the alloantigenic determinants and the beta 2 m binding site to different regions of the H-2 Kb glycoprotein.
The intramolecular organization of the membrane integrated Class I major histocompatibility complex (MHC) molecule H-2Kb (Kb) was analyzed. After the removal of the two carbohydrate moieties by glycosidase enzymes, proteolytic digestion of the Kb molecule yielded: 1) several fragments with the beta 2 microglobulin (beta 2 m) subunit still bound and 2) one fragment carrying alloantigenic activity but lacking the beta 2 m. Isolation of the beta 2 m binding fragments showed them to be derived from the C-2 domain by partial N-terminal sequence analysis. One fragment extended to the C-terminus and the other fragment had lost the transmembrane region. Such studies conclusively show that the beta 2 m subunit is bound in the third domain, i.e., C-2, of the Kb 44,000 m.w. heavy chain. The alloantigenic fragment also isolated from the proteolytic digest consists of the first 180 residues of the 44,000 m.w. heavy chain, i.e., domains N and C-1, and carried alloantigenic determinants detected by several monoclonal antibodies as well as alloantisera. The present studies indicate that the external region of the Class I molecules has two functional regions. The first 180 residues bear the recognition elements for the immune system, and the next 90 residues (180-270) are involved in binding to beta 2 m.
D000818:Animals; D000915:Antibody Affinity; D001609:Beta-Globulins / Q000276:immunology*; D001666:Binding Sites, Antibody; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D000939:Epitopes; D006023:Glycoproteins / Q000276:immunology; D006183:H-2 Antigens; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D010447:Peptide Hydrolases / Q000494:pharmacology; D011487:Protein Conformation; D001613:beta 2-Microglobulin / Q000276:immunology*
D001609:Beta-Globulins; D000939:Epitopes; D006023:Glycoproteins; D006183:H-2 Antigens; D001613:beta 2-Microglobulin; D010447:Peptide Hydrolases