IDENTIFICATION OF INFLUENZA-C VIRUS PHOSPHOPROTEINS

The HMV-II cells infected with influenza C virus were labeled with ino rganic [P-32]phosphate to identify phosphorylated proteins. Analysis b y radioimmunoprecipitation with antiviral serum or monoclonal antibodi es revealed that three major structural proteins of the virus, hemaggl utinin-esterase (HE), nucleoprotein (NP), and matrix protein (M1) are all phosphorylated in both infected cells and virions. It was also obs erved that, in the presence of trypsin (10 mu g/ml), the unphosphoryla ted form of the HE glycoprotein was cleaved efficiently whereas the ph osphorylated form was not, raising the possibility that phosphorylatio n of HE may influence its susceptibility to degradation by proteolytic enzymes.