Protein kinase associated with Newcastle disease virus

Purified virions of Newcastle disease virus (NDV) were found to contain protein kinase activity which was, like other virion-associated kinases, stimulated by Mg²⁺ and totally independent of Ca²⁺ and cAMP. The kinase phosphorylated preferentially the P and NP polypeptides of NDV. Triton-KCl fractionation of the virions has shown that the protein kinase activity may be associated with glycoprotein-free subviral particles, but not with nucleocapsids containing either only NP or some L and P proteins together with NP as protein constituent.