Varicella-zoster virus ORF47 protein serine kinase: Characterization of a cloned, biologically active phosphotransferase and two viral substrates, ORF62 and ORF63

Varicella-zoster virus (VZV) codes for a protein serine kinase called ORF47 ; the herpes simplex virus (HSV) homolog is UL13. No recombinant alphaherpe svirus serine kinase has been biologically active in vitro. We discovered t hat preservation of the intrinsic kinase activity of recombinant VZV ORF47 required unusually stringent in vitro conditions, including physiological c oncentrations of polyamines. In this assay, ORF47 phosphorylated two VZV re gulatory proteins: the ORF62 protein (homolog of HSV ICP4) and the ORF63 pr otein (homolog of HSV ICP22). Of interest, ORF47 kinase also coprecipitated ORF63 protein from the kinase assay supernatant.