Identification of platelet membrane proteins that interact with amino-terminal peptides of pp60c-src.
Platelets contain exceptionally high levels of pp60c-src and, thus, provide a convenient system for investigating the physiological function of this protein-tyrosine kinase. We have employed chemical cross-linking of myristylated amino-terminal peptides of pp60c-src to platelet membranes in order to identify platelet membrane components that interact with pp60c-src to regulate or mediate its activity. We detected specific binding of radioiodinated peptides to platelet membrane proteins of 32, 50, 92, and 105 kDa. The 32-kDa protein may be related to the putative src receptor component recently identified in fibroblast membranes. The most reactive platelet protein, however, is the 50-kDa protein, which is either absent or nonreactive in fibroblast membranes. Binding of src peptides to this protein was saturable, and we estimate the presence of approximately 1 x 10(6) of the 50-kDa binding sites per platelet. The specificity of the peptide binding to the 50- and 32-kDa platelet proteins was analyzed by competition with different peptides. The binding sites displayed an absolute requirement for an N-myristoyl moiety and a strong preference for pp60c-src amino-terminal sequences. The identification of these src-interacting proteins may help to decipher the biochemical pathways in which platelet pp60c-src is involved.
Feder
D
D
Department of Microbiology and Immunology, G. W. Hooper Research Foundation, University of California, San Francisco 94143.
Bishop
J M
JM
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000737:chemistry / Q000378:metabolism*
D001798:Blood Proteins; D008565:Membrane Proteins; D016392:Proto-Oncogene Proteins pp60(c-src)