The NS 3 nonstructural protein of flaviviruses contains an RNA triphosphatase activity.
The genome of flaviviruses consists of an infectious single-stranded RNA molecule which contains a type 1 cap structure at the 5'-terminus. The cap is synthesized by RNA triphosphatase, guanylyltransferase and methyltransferase. Since flaviviruses replicate in the cytoplasm, it can be assumed that these functions are performed by virus-coded proteins. We previously showed that subtilisin treatment of membranes isolated from cells infected with the West Nile flavivirus results in release of a 50 kDa molecular weight fragment of the viral nonstructural protein NS 3. This so-called p50-S protein contains the residue gly (168) of NS 3 at the amino-terminus and represents an RNA-stimulated NTPase. In the present report we present experimental evidence which indicates that the p50-S protein also contains the active site of an RNA triphosphatase. The activity specifically cleaves the beta,gamma-triphosphate bond at the 5'-terminus of RNA. The localization of NS 3 protein sequence elements with known functions indicates that this multifunctional protein contains a protease in the amino-terminal part, a helicase in the central region and the RNA triphosphatase in the carboxy-terminal domain. An amino acid sequence element which may be involved in recognition of the 5'-terminal RNA triphosphate is tentatively identified. A homologous element may be present in the vaccinia virus-coded RNA triphosphatase.
Wengler
G
G
Institut für Virologie, Justus-Liebig-Universität Giessen, Germany.
Wengler
G
G
D017766:Acid Anhydride Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004492:Edetic Acid / Q000494:pharmacology; D005416:Flavivirus / Q000201:enzymology / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D011061:Poly A / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D017361:Viral Nonstructural Proteins; D011061:Poly A; D004492:Edetic Acid; D017766:Acid Anhydride Hydrolases; C023090:RNA triphosphatase