RNA-dependent RNA polymerase (RdRp) in the family Togaviridae of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the RdRp of RNA viruses belonging to the family Togaviridae, order Martellivirales. Togaviridae is a family of small, enveloped viruses with [(+)ssRNA] genomes of 10-12 kb, and contains a single genus, Alphavirus. Alphavirus includes a large number of species that are mostly mosquito-borne and pathogenic in their vertebrate hosts. Many are important human and veterinary pathogens (e.g., chikungunya virus, eastern equine encephalitis virus). The genus Alphavirus mainly consists of mosquito-borne viruses although other hematophagous insects, including ticks, lice, and cliff swallow bugs, have been implicated in transmission. Vertebrate hosts include humans, non-human primates, equids, birds, amphibians, reptiles, rodents, and pigs. There are two aquatic alphaviruses, southern elephant seal virus and salmon pancreas disease virus, infecting sea mammals and fish respectively. Interestingly, Eilat virus (EILV) has been shown to only infect insect cells and is incapable of replicating in vertebrate cells. 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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