title: Tyrosine phosphorylation within the amino-terminal domain of pp60c-src molecules associated with polyoma virus middle-sized tumor antigen.
abstract: We have examined the in vitro phosphorylation of cellular src protein (pp60c-src) molecules associated with the polyoma virus middle-sized tumor antigen in polyoma virus-transformed cells. These pp60c-src molecules possessed an enhanced tyrosyl kinase activity, migrated aberrantly on NaDodSO4/polyacrylamide gels, and contained a novel site of tyrosine phosphorylation within the amino-terminal region of the molecule. The pp60c-src molecules not associated with the middle-sized tumor antigen were phosphorylated exclusively on a tyrosine residue within the carboxyl-terminal domain of pp60c-src. A similar modified form of the middle-sized tumor antigen-associated pp60c-src protein was detected in lysates from polyoma virus-transformed cells labeled in vivo with [32P]orthophosphate in the presence of sodium orthovanadate, an inhibitor of phosphotyrosyl phosphatases.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D015688:Oncogene Protein pp60(v-src); D010446:Peptide Fragments / Q000032:analysis; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D014162:Transfection; D014443:Tyrosine; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D010446:Peptide Fragments; D014764:Viral Proteins; D014443:Tyrosine; D011494:Protein Kinases; D015688:Oncogene Protein pp60(v-src)