CHARACTERIZATION OF THE INFLUENZA-VIRUS ASSOCIATED PROTEIN-KINASE AND ITS RESEMBLANCE TO CASEIN KINASE-II

The protein kinase activity associated with purified influenza virus has been examined. By use of a radiolabelled photoreactive ATP analogue (3'-O-(4 benzoyl) benzoyl adenosine triphosphate) a 47 kD polypeptide has been identified that binds ATP. A comparison of the sensitivity of the kinase activity and the 47 kDa polypeptide labelling to inhibitors indicate that the 47 kDa polypeptide is likely to represent the major protein kinase activity of the virus. The virus associated protein kinase phosphorylates the synthetic peptide RREEETEEE, a peptide substrate for casein kinase II. Antiserum directed against casein kinase II revealed a positive signal in immunoblots of purified virus. We propose that the major protein kinase activity associated with purified virus preparations is host cell casein kinase II.