Protein kinase activity in purified poliovirus particles and empty viral capsid preparations

Preparations of purified poliovirus type 1, strain Mahoney, and empty viral capsids contain a protein kinase activity. The gamma-phosphoryl group of [32P]ATP is transferred to all of the capsid proteins. Viral proteins phosphorylated in vitro are recognized by antiserum directed against isolated viral capsid proteins, indicating that phosphorylation does not alter the antigenic sites to such an extent that the recognition by antibodies is abolished. Viral capsid protein phosphorylation exposes new antigenic sites and leads to a destabilization of the virions. The transfer of 32P to viral proteins is linear for 90 min at 37 degrees C in the presence of 10 mM-Mg2+ at pH 8.1. Reducing agents or virus-stabilizing agents (such as arildone) reduce the kinase activity and result in a different pattern of capsid protein phosphorylation.