Protein kinase in nondiabetogenic coxsackievirus B4

Alkali-dissociated, purified preparations of prototype coxsackievirus B4 release a protein kinase that catalyzes the incorporation of gamma-phosphate from 32P-labeled ATP into three virus capsid proteins (VP1, VP3, VP4), several additional proteins of the particle, and exogenous acceptor proteins. Using protamine sulfate as an acceptor protein, we detected nearly 20-fold more enzyme activity in membrane-bound virions (MBV) than in virions of the virus. The activity in the MBV is cyclic nucleotide-independent, divalent cation-dependent, and has a pH optimum of 8.0. Phosphoserine is labeled with 32P. The enzyme activity sediments at about 5S and is separated into at least two peaks of heterogeneous proteins by ion-exchange chromatography. The patterns of phosphorylation by these enzyme peaks are somewhat similar. Coxsackievirus-associated protein kinase appears to be located internally in the virus and may be host-cell-coded. The enzyme appears to be lacking in a variant of the virus that produced diabetes in mice.