catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the genus Sapelovirus of positive-sense single-stranded RNA [(+)ssRNA] viruses, within the family Picornaviridae
This group contains the catalytic core domain of the RdRp of RNA viruses belonging to the Sapelovirus genus within the family Picornaviridae, order Picornavirales. Member viruses have a (+)ssRNA genome. Viruses in Sapelovirus are non-enveloped, with icosahedral, spherical, and round geometries, and T=pseudo3 symmetry. Sapelovirus, formerly known as porcine enterovirus (PEV)-8, is known to infect pigs asymptomatically but can cause reproductive failure and severe neurologic, enteric, or respiratory signs. Sapelovirus infections have been reported worldwide in pigs. The genus Sapelovirus contains three species, with a unique genome organization: Sapelovirus A, also known as porcine sapelovirus (PSV); Sapelovirus B as simian sapelovirus; and Avian sapelovirus represented by duck picornavirus. 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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