catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the family Roniviridae of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the catalytic core domain of RdRp of RNA viruses belonging to the family Roniviridae, order Nidovirales. Member viruses have a viral envelope and (+)ssRNA genome. The family Roniviridae includes a single genus (Okavirus) for three species of viruses (Yellow head virus, Gill-associated virus and Okavirus 1) with enveloped, rod-shaped virions. Roniviruses infect penaeid and palaemonid shrimp. Natural infections are usually without apparent clinical signs. One member of the family (yellow head virus) is highly pathogenic for shrimp. Roniviruses are most closely related to other nidoviruses infecting arthropods, including members of the families Mesoniviridae (from mosquitoes) and Euroniviridae (from crustaceans). The structure of Roniviridae RdRp contains a RdRp domain as well as a large N-terminal extension that adopts a nidovirus RdRp-associated nucleotidyltransferase (NiRAN) architecture. 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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