Phosphoproteins, structural components of rhabdoviruses.

Abstract

Abstract Polypeptides derived from purified rabies, vesicular stomatitis, and Kern Canyon viruses, which were labeled with 3H-amino acids and 32P-phosphate, were subjected to electrophoretic fractionation in order to determine which of the structural proteins is phosphorylated. In the rabies virion, the nucleocapsid protein (N protein) was found to be phosphorylated, whereas the other three virus proteins were not. N protein of free viral nucleocapsids isolated from rabies virus-infected cells was also phosphorylated. The phosphorylation of the N protein of rabies virus is confined to a relatively small terminal segment of the polypeptide chain which can be specifically cleaved off by treatment of the nucleocapsid with trypsin. In vesicular stomatitis virus the minor NS protein component is the only phosphoprotein. In Kern Canyon virus the envelope glycoprotein and the N protein are both phosphorylated, but to a lesser extent than either the N protein of rabies virus or the NS protein of vesicular stomatitis virus. All three rhabdoviruses contain a virion-bound protein kinase. Free nucleocapsids derived from rabies virus-infected cells and purified by equilibrium centrifugation in CsCl solution also contain a protein kinase. Intracellular nucleocapsids of vesicular stomatitis or Kern Canyon viruses do not exhibit protein kinase activity.