catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the genus Parechovirus of positive-sense single-stranded RNA [(+)ssRNA] viruses, within the family Picornaviridae
This group contains the catalytic core domain of RdRp of RNA viruses belonging to the Parechovirus genus within the family Picornaviridae, order Picornavirales. Member viruses have a (+)ssRNA genome. The Parechovirus genus is comprised of six species, Parechovirus A (formerly named Human parechovirus), Parechovirus B (formerly named Ljungan virus), Parechovirus C (Sebokele virus) and Parechovirus D (ferret parechovirus), Parechovirus E (falcon parechovirus) and Parechovirus F (gecko parechovirus). Humans, ferrets, and various rodents serve as natural hosts. Human parechoviruses may cause gastrointestinal or respiratory illness in infants, and have been implicated in cases of myocarditis and encephalitis. Human parechoviruses replicate in the respiratory and gastrointestinal tract. 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 picornaviruses. 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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