RNA-dependent RNA polymerase (RdRp) in the genus Hepatovirus of positive-sense single-stranded RNA [(+)ssRNA] viruses, within the family Picornaviridae
This group contains the RdRp of RNA viruses belonging to the Hepatovirus genus within the family Picornaviridae, order Picornavirales. Hepatoviruses are 27- to 32-nm, nonenveloped, icosahedral viruses with a (+)ssRNA linear genome of approximately 7.5-kb. The Hepatovirus genus has nine species, Hepatovirus A-I, of which Hepatovirus A is responsible for a self-limiting viral hepatitis in human beings and may be transmitted by the fecal-oral route during acute infection or by the ingestion of uncooked contaminated shellfish. RdRps are multi-domain proteins that play a pivotal role in enterovirus replication. RdRps catalyze RNA template-dependent formation of phosphodiester bonds between ribonucleotides in the presence of divalent metal ions. The initiation of synthesis occurs at the 3'-end of the template in a VPg-dependent manner, and proceeds in the direction of 5'-3'. The active sites of RdRps are highly conserved in different species of hepatoviruses. 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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