Purification of the Rous sarcoma virus src kinase by casein-agarose and tyrosine-agarose affinity chromatography

A simple and effective purification method for the src kinase, the transforming gene product of Rous sarcoma virus, has been developed by using affinity chromatography on casein-agarose and tyrosine-agarose columns. NaDodSO4/polyacrylamide gel electrophoresis and silver staining analysis showed that the purified kinase preparation was composed of a predominant polypeptide of 60,000-Da. In most of the preparations, however, three minor proteins (54,000, 52,000, and 15,000 Da) were also detected, and they were partially characterized. As one of the exogenous substrates, calmodulin was found to be phosphorylated on tyrosine by the purified src kinase.