catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the family Tombusviridae of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the catalytic core domain of RdRp of RNA viruses belonging to the family Tombusviridae, order Tolivirales. The family Tombusviridae comprises plant viruses, and is classified into 3 subfamilies (Calvusvirinae, Procedovirinae, and Regressovirinae), 17 genera, and 95 species. One genus is unassigned to a subfamily: Luteovirus. The name of the family is derived from Tomato bushy stunt virus (TBSV). Members of Tombusviridae replicate in the cytoplasm, by use of negative strand templates. The replication process leaves a surplus of positive- sense (+)RNA strands, and it is thought that not only does the viral RNA act as a template for replication, but is also able to manipulate and regulate RNA synthesis. 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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