Protein kinase activity associated with simian virus 40 T antigen.

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Abstract
Incubation of SV-40 tumor (T) antigen-containing immunoprecipitates with [.gamma.-32P]ATP results in the incorporation of radioactive phosphate into large T antigen. Highly purified preparations of large T antigen from a SV-40-transformed cell line, SV80, are able to catalyze the phosphorylation of a known phosphate acceptor, casein. The kinase activity migrates with large T antigen through multiple purification steps. Sedimentation analysis under non-T-antigen-aggregating conditions reveals that kinase activity and the immunoreactive protein comigrate as a 6S structure. The kinase activity of purified preparations of large T antigen can be specifically adsorbed to solid-phase anti-T Ig[immunoglobulin]G, and partially purified T antigen from a SV-40 tsA transformant is thermolabile in its ability to phosphorylate casein when compared to comparably purified wild-type T antigen. These observations indicate that the SV-40 large T antigen is closely associated with protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) activity.