Protein Kinase Activity in Purified Poliovirus Particles and Empty Viral Capsid Preparations

Preparations ofpurified poliovirus type 1, strain Mahoney, and empty viral capsids contain aprotein kinase activity. The y-phosphoryl group of [32p]AT P 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 phosphoryla-tion does not alter the antigenic sites to such an extent that the recognition by antibodies i abolished. Viral capsid protein phosphorylation exposes new antigenic sites and leads to a destabilization f the virions. The transfer of 32p to viral proteins is linear for 90 min at 37 °C in the presence of 10 mM-Mg 2 + at pH 8-1. Reducing agents or virus-stabilizing agents (such as arildone) reduce the kinase ctivity and result in a different pattern of capsid protein phosphorylation