title: A novel 53 kDa protein complexed with P210bcr-abl in human chronic myelogenous leukemia cells.
abstract: Leukemic cells from patients with Philadelphia chromosome (Ph1)-positive chronic myelogenous leukemia (CML) contain a 210 kDa protein (P210bcr-abl) with a protein tyrosine kinase activity that is a product of fused bcr and abl genes. We have prepared two monoclonal anti-peptide antibodies, one from each gene product, and have affinity purified each. Incubation of anti-abl (c-abl 51-64) immunoprecipitates of K562 cells with [gamma-32P]ATP in protein kinase assays resulted in the labeling of P210bcr-abl and a 53 kDa (ph-P53) protein. Increasing concentrations of antibody detected similar ratios of P210bcr-abl: ph-P53, suggesting the presence of a complex between the proteins. Several different anti-abl and anti-bcr antibodies detected the ph-P53/P210 complex. Sodium dodecyl sulfate (SDS) treatment without 2-mercaptoethanol eluted P210bcr-abl and ph-P53 from the monoclonal antibody in the form of complexes which migrated on 6% SDS-polyacrylamide gels and had apparent molecular weights of 275,000 and more than 500,000. Both complexes yielded ph-P53 and P210bcr-abl upon treatment with SDS-mercaptoethanol. Studies involving glycerol gradient centrifugation also detected complexes of P210bcr-abl and ph-P53. Our results indicate that ph-P53 is not a degraded product of P210bcr-abl, does not share antigenic determinants with P210bcr-abl since it is not recognized by anti-abl and bcr antibodies in immunoblots, is not the phosphorylated heavy chain of immunoglobulin G, and is different from p53 (the nonviral T protein) complexed to the large T antigen of simian virus 40. Previous studies (Maxwell et al., 1987) have shown that ph-P53 has a different peptide map than P210bcr-abl. Therefore, we conclude that ph-P53 is a distinct cellular protein complexed to P210bcr-abl in K562 cells.
mesh_terms: D002458:Cell Fractionation; D004591:Electrophoresis, Polyacrylamide Gel; D016044:Fusion Proteins, bcr-abl; D006801:Humans; D007158:Immunologic Techniques; D007951:Leukemia, Myeloid / Q000378:metabolism*; D046911:Macromolecular Substances; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D016044:Fusion Proteins, bcr-abl