Purified EGF receptor–kinase interacts specifically with antibodies to Rous sarcoma virus transforming protein

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Abstract
Transformation by several RNA tumor viruses seems to be mediated by virally-coded protein kinases which specifically phosphorylate tyrosine. A tyrosine-specific protein kinase also seems to be involved in the mitogenic action of epidermal growth factor (EGF). This EGF-stimulated kinase activity is closely associated with the EGF receptor with which it co-purifies during EGF-affinity chromatography. Because both the virus- and EGF-stimulated tyrosine kinases may be involved in stimulation of cell growth, and the viral kinases may be antigenically related to normal cell proteins, the interaction of antibodies to viral tyrosine kinases with the affinity-purified EGF receptor-kinase preparation was examined. The receptor-kinase specifically phosphorylates antibodies directed against the transforming protein kinase pp60src of Rous sarcoma virus. However, none of these antibodies, including those which cross-react with the normal cellular homolog of pp60src (pp60sarc), precipitate the receptor-kinase. The EGF receptor-kinase may be related to, but is probably not identical with, pp60sarc.