Identification of a Rous sarcoma virus transformation-related protein in normal avian and mammalian cells.

Abstract

Avian sarcoma viruses (ASV) contain a gene (src) whose protein product mediates sarcomagenic transformation. This product is a 60,000-MW phosphoprotein designated pp60src. Normal uninfected frog, chicken, rat and human cells contain a 60,000-MW phosphoprotein related to the product of the ASV src gene and designated that protein pp60. A phosphoprotein of similar size was not detectable in Drosophila cells. The pp60 proteins were detected by immunoprecipitation with rabbit antitumor serum containing broad spectrum antibodies to pp60src. Peptide maps of [35S]-methionine-labeled pp60 and pp60src indicated major similarities and some differences in amino acid composition. Peptide maps of the 32P-labeled proteins demonstrated that the phosphopeptides of all endogenous pp60 molecules tested were identical. Some differences were noted between the phosphopeptide patterns of pp60 and viral pp60src. The kinase activity associated with pp60src was measured in the immunocomplex and resulted in the transfer of radioactive P from [.gamma.-32P]ATP to immunoglobulin heavy chain and to an 80,000-MW phosphoprotein. The pp60 of chicken, rat and human origin also contained an associated kinase activity. The pp60 molecules are apparently the protein products of endogenous sarc sequences found in vertebrate cells.