2ckw
The 2.3 A resolution structure of the Sapporo virus RNA dependant RNA polymerase.
Structural highlights
FunctionPOLG_SVM93 NTPase presumably plays a role in replication. Despite having similarities with helicases, does not seem to display any helicase activity (By similarity). Viral genome-linked protein is covalently linked to the 5'-end of the positive-strand, negative-strand genomic RNAs and subgenomic RNA. Acts as a genome-linked replication primer. May recruit ribosome to viral RNA thereby promoting viral proteins translation (By similarity). Protease-polymerase processes the polyprotein: Pro-Pol is first released by autocleavage, then all other proteins are cleaved (By similarity). Protease-polymerase is a RNA-directed RNA polymerase which replicates genomic and antigenomic viral RNA by recognizing specific signals. Catalyzes the covalent attachment VPg with viral RNAs (By similarity). Capsid protein self assembles to form an icosahedral capsid with a T=3 symmetry, about 38 nm in diameter, and consisting of 180 capsid proteins. The capsid encapsulate the genomic RNA and VP2 proteins. Attaches virion to target cells, inducing endocytosis of the viral particle. Acidification of the endosome induces conformational change of capsid protein thereby injecting virus genomic RNA into host cytoplasm (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSapoviruses are one of the major agents of acute gastroenteritis in childhood. They form a tight genetic cluster (genus) in the Caliciviridae family that regroups both animal and human pathogenic strains. No permissive tissue culture has been developed for human sapovirus, limiting its characterization to surrogate systems. We report here on the first extensive characterization of the key enzyme of replication, the RNA-dependent RNA polymerase (RdRp) associated with the 3D(pol)-like protein. Enzymatically active sapovirus 3D(pol) and its defective mutant were expressed in Escherichia coli and purified. The overall structure of the sapovirus 3D(pol) was determined by X-ray crystallography to 2.32-A resolution. It revealed a right hand fold typical for template-dependent polynucleotide polymerases. The carboxyl terminus is located within the active site cleft, as observed in the RdRp of some (norovirus) but not other (lagovirus) caliciviruses. Sapovirus 3D(pol) prefers Mn(2+) over Mg(2+) but may utilize either as a cofactor in vitro. In a synthetic RNA template-dependent reaction, sapovirus 3D(pol) synthesizes a double-stranded RNA or labels the template 3' terminus by terminal transferase activity. Initiation of RNA synthesis occurs de novo on heteropolymeric templates or in a primer-dependent manner on polyadenylated templates. Strikingly, this mode of initiation of RNA synthesis was also described for norovirus, but not for lagovirus, suggesting structural and functional homologies in the RNA-dependent RNA polymerase of human pathogenic caliciviruses. This first experimental evidence makes sapovirus 3D(pol) an attractive target for developing drugs to control calicivirus infection in humans. Structural and functional characterization of sapovirus RNA-dependent RNA polymerase.,Fullerton SW, Blaschke M, Coutard B, Gebhardt J, Gorbalenya A, Canard B, Tucker PA, Rohayem J J Virol. 2007 Feb;81(4):1858-71. Epub 2006 Nov 22. PMID:17121797[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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