NS2 protein of influenza virus is found in purified virus and phosphorylated in infected cells

Summary Purified viral preparations of influenza A virus were examined for the presence of NS₂ protein hitherto considered as a viral nonstructural protein that is present only in infected cells. Analysis of purified virus by radioimmunoprecipitation with monospecific antisera to NS₂ revealed its presence in the virus particle suggesting that it is a viral structural protein. NS₂ protein was also shown to be phosphorylated in infected cells in this study. This brings the number of influenza virus phosphoproteins to three which include NP, NS₁, and NS₂. These observations raise important questions about the role of NS₂ in the replication of influenza virus.