Varicella zoster virus glycoprotein gpI is selectively phosphorylated by a virus-induced protein kinase.

Varicella zoster virus glycoprotein I (VZV gpI; Mr 98,000) was phosphorylated in virus-infected human cell monolayers, while two other major VZV glycoproteins (gpII and gpIII) were not similarly modified. Phosphorylation of VZV gpI was not blocked by inhibitors of glycosylation, nor were the phosphoryl groups enzymatically removed by endoglycosidases. Phosphoamino acid analysis revealed the presence of phosphoserine and phosphothreonine residues on the polypeptide backbone. The selective nature of the phosphorylation event was further demonstrated in vitro by a protein kinase (Mr 50,000), which was present in virus-infected cells but absent from uninfected cells or purified virions. The enzyme catalyzed the transfer of 32Pi from [gamma-32P]ATP to gpI but not to gpII and gpIII. Like VZV gpI, this virus-induced protein kinase was also a constituent of the plasma membrane of live VZV-infected cells.