RNA-dependent RNA polymerase (RdRp) in the genus Megrivirus of positive-sense single-stranded RNA [(+)ssRNA] viruses, within the family Picornaviridae
This group contains the RdRp of RNA viruses belonging to the Megrivirus genus within the family Picornaviridae, order Picornavirales. The Megrivirus contains viruses with (+)ssRNA genomes that produce nonenveloped virions. The genus Megrivirus contains a five species Megrivirus A, Megrivirus B, Megrivirus C, Megrivirus D and Megrivirus E. The name Megrivirus is derived from the turkey genus name Meleagris. Megrivirus A is comprised of turkey hepatitis virus 1 (THV-1), duck megrivirus and goose megrivirus 1. Megrivirus B contains the mesiviruses. Megrivirus D contains harrier picornavirus 1 (HaPV-1). Megrivirus E was found in an Adelie penguin. 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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