Identification and characterization of the RNA helicase activity of Japanese encephalitis virus NS3 protein

The NS3 protein of Japanese encephalitis virus (JEV) contains motifs typica l of RNA helicase/NTPase but no RNA helicase activity has been reported for this protein. To identify and characterize the RNA helicase activity of JE V NS3, a truncated form of the protein with a His-tag was expressed in Esch erichia coli and purified. The purified JEV NS3 protein showed an RNA helic ase activity. which was dependent on divalent cations and ATP, An Asp-285-t o-Ala substitution in motif II. of the JEV NS3 protein abolished the ATPase and RNA helicase activities, These results indicate that the C-terminal 45 7 residues are sufficient to exhibit the RNA helicase activity of JEV NS3. (C) 2000 Federation of European Biochemical Societies.