RNA-dependent RNA polymerase (RdRp) in the genus Cosavirus of positive-sense single-stranded RNA [(+)ssRNA] viruses, within the family Picornaviridae
This group contains the RdRp of RNA viruses belonging to the Cosavirus genus within the family Picornaviridae, order Picornavirales. The Cosavirus contains viruses with (+)ssRNA genomes that produce nonenveloped virions. This genus consists of five species Cosavirus A, Cosavirus B, Cosavirus D, Cosavirus E and Cosavirus F. The candidate species, Cosavirus C, remains unclassified due to a lack of full genome sequence data. Cosaviruses (formerly called Dekaviruses) have been identified in the stools of south Asian children. Cosaviruses are most closely related to members of the Cardiovirus and Senecavirus genera, but they lack a leader polypeptide. The name Cosavirus stands for common stool-associated 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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