Immunological characterization of proteins detected by phosphotyrosine antibodies in cells transformed by Rous sarcoma virus.

Phosphotyrosine antibodies were used to identify tyrosine-phosphorylated proteins in Rous sarcoma virus (RSV)-transformed chicken embryo fibroblasts. A large number of tyrosine phosphoproteins were detected. A similar set of proteins was observed in RSV-transformed murine cells. An 85,000-dalton protein, however, was present in transformed avian cells but missing in transformed murine cells. Neither the 85,000-dalton protein nor any of the other tyrosine phosphoproteins appeared to be viral structural proteins. Use of RSV mutants encoding partially deleted src gene products enabled us to identify a 60,000-dalton cellular tyrosine phosphoprotein that comigrated with wild-type pp60v-src. With the exception of calpactin I, the major tyrosine phosphoproteins detected in immunoblots appeared to be different from several previously characterized substrates of pp60v-src with similar molecular masses (ezrin, vinculin, and the fibronectin receptor).