catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the subfamily Calvusvirinae of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the catalytic core domain of the RdRp of RNA viruses belonging to the subfamily Calvusvirinae, family Tombusviridae, order Tolivirales. Umbravirus is a genus of plant viruses assigned to this subfamily. The genus includes nine distinct virus species: Carrot mottle mimic virus (CMoMV), Groundnut rosette virus (GRV), Ethiopian tobacco bushy top virus (ETBTV), Lettuce speckles mottle virus (LSMV), Opium poppy mosaic virus (OPMV), Pea enation mosaic virus-2 (PEMV-2), Tobacco mottle virus (TMoV), and Tobacco bushy top virus (TBTV). Umbraviruses differ from other plant viruses in that they do not encode a coat protein (CP), and thus no conventional virus particles are formed in the infected plants. However, they encode RdRp domain typical to that of other members of the family Tombusviridae, allowing to classify the genus Umbravirus within this family. The RdRp domain displays a right hand with three functional subdomains, called fingers, palm, and thumb. All RdRps contain conserved polymerase motifs (A-G), located in the palm (A-E motifs) and finger (F-G) subdomains. All these motifs have been implicated in RdRp fidelity such as processes of correct incorporation and reorganization of nucleotides.
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