Preferential phosphorylation of NP-protein of influenza A2 virus by virion-associated protein kinase.

Influenza A2 virions were found to contain protein kinase activity which was stimulated, like in other virion-associated kinases, with Mg++ and Nonidet-P 40 but not with cyclic AMP. The kinase phosphorylated only the NP-protein fraction of the influenza virions in the in vitro reaction. In contrast, none of the influenza virion proteins were phosphorylated significantly during the process of virus production in infected chorioallantoic membranes. The in vitro and in vivo phosphorylations of influenza viral proteins were compared with those of Sendai virus (HVJ).