Purification and characterization of two protein kinases associated with Rous sarcoma virus

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Abstract
The 2 major phosvitin-utilizing kinases were purified from virions of the Prague C strain of Rous sarcoma virus by the use of ion-exchange and affinity chromatography. The 2 kinases isolated may be differentiated by their MW and by their ability to utilize GTP as a phosphate donor. Protein kinase G, which will use either GTP or ATP as a phosphate donor, has a MW of 120,000 as determined under nondenaturing conditions by glycerol gradient centrifugation and 28,000 when assayed under denaturation in sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gels. Protein kinase A, which will only efficiently use ATP as the phosphate donor, has an apparent MW of 43,000 estimated by glycerol gradient sedimentation and 40,000 by NaDodSO4-polyacrylamide electrophoresis. Both kinases possess the ability to autophosphorylate. Phosvitin is the major, and casein the minor, phosphate-accepting substrate for both kinases in vitro; kinase G will also phosphorylate histones to an extent similar to that observed with casein.