Purification of the structural and nonstructural proteins of St. Louis encephalitis virus

We have developed a procedure for purifying both the structural and nonstructural proteins of flaviviruses from lysates of infected cell cultures. The procedure involves: (l)immunoprecipitation to concentrate viral proteins and eliminate most of the cellular proteins, (2) preparative polyacrylamide gel electrophoresis to separate the viral proteins, and (3) hydroxyapatite chromatography, which eliminates most of the unlabeled cellular protein. This procedure offers an improvement over previous purification schemes in that there is no loss of viral proteins after the immunoprecipitation step, any combination of labeling isotopes may be used, and it is not necessary to soak proteins out of gel slices.