Characterization of a protein kinase gene from two Chlorella viruses

An open reading frame (ORF) with strong homology to eukaryotic serine/threonine protein kinases was found in the two Chlorella viruses SC-1A and PBCV-1. The deduced molecular weights of each putative protein kinase were 35 kDa and the predicted amino acid sequences of the two proteins were 95% identical. The ORF encoding the SC-1A protein kinase was over-expressed as a fusion protein in Escherichia coli. The recombinant fusion protein had autophosphorylation activity and could phosphorylate certain exogenous proteins. Antiserum against the recombinant fusion protein reacted with a 35 kDa protein plus three larger proteins from virus infected cells. The 35 kDa protein was a late protein; however, the 35 kDa protein was not packaged in the virion, even though virions contain protein kinase activity.