Coronavirus JHM: a virion-associated protein kinase.

Coronavirus JHM contains six major proteins, one of which, the 60 000 mol. wt. nucleocapsid protein pp60, is phosphorylated. In JHM-infected cells ip 60K, the intracellular precursor to pp60 is also phosphorylated. Associated with purified JHM virions is a protein kinase which will phosphorylate pp60 and a variety of exogenous substances in vitro. The enzyme has the characteristics of a cyclic nucleotide-independent protein kinase. Both the in vivo reaction and the enzyme activity in vitro transferred the gamma-phosphate of ATP to serine residues on the nucleocapsid protein.