title: Comparison of the 34,000-Da pp60src substrate and a 38,000-Da phosphoprotein identified by monoclonal antibodies.
abstract: One of the cellular targets of the pp60src tyrosine kinase is a phosphoprotein with a Mr = 34,000 and an isoelectric point of approximately 7.5 (Radke, K., Gilmore, T., and Martin, G. S. (1980) Cell 21, 821-828; Erikson, E., and Erikson, R. L. (1980) Cell 21, 829-836). We report here the preparation of monoclonal antibodies to partially purified 34-kDa protein and to a heretofore unrecognized phosphoprotein that is not a pp60src target. Two antibodies were initially obtained that recognized phosphoproteins in the Mr = 34,000-39,000 range. One of these antibodies immunoprecipitated a 34,000-Da protein which, on the basis of its molecular mass, phosphorylation state, and isoelectric point, was determined to be the 34-kDa pp60src substrate. The second monoclonal antibody bound to a 38,000-Da nucleolar associated protein, which appeared not to be a target of the pp60src kinase and was found by tryptic analysis to be structurally unrelated to the 34-kDa protein. The monoclonal antibody to the 34-kDa protein coupled to Sepharose CL-4B was used to purify the pp60src substrate to homogeneity in milligram quantities. Both the purified 34-kDa protein and the monoclonal antibody are currently being used in studies aimed at elucidating the structure and function of this pp60src target.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D001358:Avian Sarcoma Viruses / Q000235:genetics; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D002642:Chick Embryo; D005347:Fibroblasts; D008970:Molecular Weight; D015688:Oncogene Protein pp60(v-src); D010750:Phosphoproteins / Q000032:analysis* / Q000276:immunology; D011494:Protein Kinases / Q000032:analysis* / Q000276:immunology; D014764:Viral Proteins / Q000032:analysis* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D010750:Phosphoproteins; D014764:Viral Proteins; D011494:Protein Kinases; D015688:Oncogene Protein pp60(v-src)