catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the family Secoviridae of positive-sense single-stranded RNA [(+)ssRNA] viruses, in the order Picornavirales
This group contains the catalytic core domain of RdRp of RNA viruses belonging to the family Secoviridae, order Picornavirales. Members of the family Secoviridae are non-enveloped viruses with mono- or bipartite (RNA-1 and RNA-2) linear (+)ssRNA genomes of 9 to 13.7 kilobases in total. Secoviruses are related to picornaviruses and are classified in the order Picornavirales. The majority of known members infect dicotyledonous plants and many are important plant pathogens (e.g., grapevine fanleaf virus and rice tungro spherical virus). The Secoviridae includes 8 genera (Comovirus, Fabavirus, Nepovirus, Cheravirus, Sadwavirus, Torradovirus, Sequivirus, and Waikavirus) as well as unassigned species (strawberry latent ringspot virus-MEN 454, strawberry mottle virus-Thompson, black raspberry necrosis virus- 1, chocolate lily virus A-KP2, and Dioscorea mosaic associated virus-goiana). 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",