Isolation and characterization of the ribonucleoprotein of influenza virus

Treatment of the WSN strain of influenza virus with the non-ionic detergent nonidet P-40, followed by velocity gradient centrifugation, yielded a ribonucleoprotein (RNP) with a sedimentation constant of about 38 S. This 38 S RNP, which consisted of 10% RNA and 90% protein, contained the five pieces of RNA previously found by extracting the virus with phenol-SDS. The RNA in the 38 S complex, although less susceptible to RNase digestion than was 20 S RNA, could be completely degraded by prolonged treatment with the enzyme. The 20 S RNA could be obtained from the 38 S RNP by treating the RNP with polyvinylsulfate (PVS). The PVS replaced the RNA on the protein and the PVS-protein complex sedimented at 38 S. The protein portion of the RNP appears to be a single component as shown by gel electrophoresis. Electron micrographs are presented which show the structure of the RNP and which support conclusions drawn from the biochemical data.