catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the family Kitaviridae of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the catalytic core domain of RdRp of RNA viruses belonging to the family Kitaviridae, order Martellivirales. The family Kitaviridae is composed of five recognized species among the three genera: Blueberry necrotic ring blotch virus and Tea plant necrotic ring blotch virus (genus Blunervirus); Citrus leprosis virus C and Citrus leprosis virus C2 (genus Cilevirus); and Hibiscus green spot virus 2 (genus Higrevirus). Although related, there are considerable physical and genetic distinctions between members of the different genera. For example, cile- and higreviruses are associated with a bacilliform virion, whereas a spherical virion has been observed for the lone blunervirus for which microscopy has been reported. Moreover, the replication-associated polyproteins are encoded by a single genomic RNA for cile- and higreviruses, but are split between two genomic RNAs for blunerviruses. 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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