title: Human class I histocompatibility antigens (HLA-A,B,C). A small proportion only is phosphorylated.
abstract: Human Class I HLA antigens (HLA-A,B,C) were isolated by immune precipitation from cells labelled with 32P, [35S]methionine or 125I (by lactoperoxidase-catalysed cell-surface iodination) and were analysed using both one- and two-dimensional electrophoretic systems. In several B-lymphoblastoid cell lines and in human peripheral blood lymphocytes the electrophoretic mobility of the 32P-labelled HLA-A,B,C heavy chains consistently differed from that of molecules labelled by other means. Thus the 32P-labelled heavy chains appeared to be larger and to possess a more acidic pI than did heavy chains labelled with [35S]methionine or 125I, or identified by Coomassie Blue staining. Phosphatase treatment of immunoprecipitates, under conditions where 32P-labelled antigens were shown to be dephosphorylated, did not affect the mobilities of the [35S]methionine-labelled heavy chains. On glycosidase treatment, the positions of the 32P-labelled heavy chains were affected by neuraminidase but not by endo-beta-N-acetylglucosaminidase H. These results imply that phosphorylated HLA-A,B,C antigens comprise only a small proportion (relative to the total cellular HLA-A,B,C antigens) of the biosynthetically mature molecules. The possible significance of such heterogeneity is discussed.
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology; D002051:Burkitt Lymphoma / Q000276:immunology; D002460:Cell Line; D011232:Chemical Precipitation; D004591:Electrophoresis, Polyacrylamide Gel; D006680:HLA Antigens; D015234:HLA-A Antigens; D015235:HLA-B Antigens; D015236:HLA-C Antigens; D006801:Humans; D008214:Lymphocytes / Q000276:immunology*; D010744:Phosphoric Monoester Hydrolases; D010766:Phosphorylation
chemical_list: D006680:HLA Antigens; D015234:HLA-A Antigens; D015235:HLA-B Antigens; D015236:HLA-C Antigens; D010744:Phosphoric Monoester Hydrolases