Protein kinase and specific phosphate acceptor proteins associated with vaccinia virus cores

Incubation of purified vaccinia virus with gamma-(32)P-adenosine triphosphate resulted in the incorporation of (32)P into hot trichloroacetic acid-insoluble material. Enzymatic activity was completely dependent on the addition of divalent cations and was stimulated by nonionic detergents and dithiothreitol. Chemical studies demonstrated that serine and threonine residues of 15,000 molecular weight viral polypeptides were phosphorylated. In contrast, the major structural proteins were not phosphorylated or were phosphorylated to a much lesser extent. Added histones and protamine, but not serum albumin, casein, or phosvitin were phosphorylated by the partially disrupted vaccinia virus preparations. The protein kinase was tightly associated with vaccinia virus particles since the specific enzymatic activity remained constant during the final steps of virus purification, the specific activities of many different preparations of virus were similar, and the enzymatic activity cosedimented with vaccinia virus during rate zonal sucrose gradient and potassium tartrate gradient equilibrium centrifugations. Controlled degradation of vaccinia virus, with nonionic detergents and dithiothreitol, indicated that both the protein kinase and the specific phosphate acceptor proteins were located in the virus core.