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Structure and Function of Flavivirus NS5 Methyltransferase.
- Source :
-
Journal of Virology . Apr2007, Vol. 81 Issue 8, p22-22. 1p. - Publication Year :
- 2007
-
Abstract
- The plus-strand RNA genome of flavivirus contains a 5′ terminal cap 1 structure (m7GpppAmG). The flaviviruses encode one methyltransferase, located at the N-terminal portion of the NS5 protein, to catalyze both guanine N-7 and ribose 2′-OH methylations during viral cap formation. Representative flavivirus methyltransferases from dengue, yellow fever, and West Nile virus (WNV) sequentially generate GpppA →m7GpppA →m7GpppAm. The 2′-O methylation can be uncoupled from the N-7 methylation, since m7GpppA-RNA can be readily methylated to m7GpppAm-RNA. Despite exhibiting two distinct methylation activities, the crystal structure of WNV methyltransferase at 2.8 Å resolution showed a single binding site for S-adenosyl-L-methionine (SAM), the methyl donor. Therefore, substrate GpppA-RNA should be repositioned to accept the N-7 and 2′-O methyl groups from SAM during the sequential reactions. Electrostatic analysis of the WNV methyltransferase structure showed that, adjacent to the SAM-binding pocket, is a highly positively charged surface that could serve as an RNA binding site during cap methylations. Biochemical and mutagenesis analyses show that the N-7 and 2′-O cap methylations require distinct buffer conditions and different side chains within the K61-D146-K182-E218 motif, suggesting that the two reactions use different mechanisms. In the context of complete virus, defects in both methylations are lethal to WNV; however, viruses defective solely in 2′-O methylation are attenuated and can protect mice from later wild-type WNV challenge. The results demonstrate that the N-7 methylation activity is essential for the WNV life cycle and, thus, methyltransferase represents a novel target for flavivirus therapy. [ABSTRACT FROM AUTHOR]
- Subjects :
- *RNA
*GENOMES
*FLAVIVIRUSES
*METHYLTRANSFERASES
*METHYLATION
*METHYL groups
Subjects
Details
- Language :
- English
- ISSN :
- 0022538X
- Volume :
- 81
- Issue :
- 8
- Database :
- Academic Search Index
- Journal :
- Journal of Virology
- Publication Type :
- Academic Journal
- Accession number :
- 24841520
- Full Text :
- https://doi.org/10.1128/JVI.02704-06