catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the order Alphatetraviridae of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the catalytic core domain of RdRp of RNA viruses belonging to the family Alphatetraviridae, order Hepelivirales. The Alphatetraviridae is a family of (+)ssRNA viruses with nonenveloped icosahedral T=4 viral particles; they restrictively infect insects, particularly the Lepidoptera. The Alphatetraviridae family includes two genera representing viruses with a monopartite (Betatetravirus) and bipartite (Omegatetravirus) genome organization. Under a previous classification, this Alphatetraviridae family was included in a single group of tetraviruses along with two other families: Carmotetraviridae (single species) and Permutotetraviridae. Neither of these two families is now included in this Alphatetraviridae family: Carmotetraviridae is now classified into a different order, Tolivirales; Permutotetraviridae is a permuted RdRp and not included in this RdRp hierarchy. Alphatetravirus replicases include three conserved functional domains, namely methytransferase (MT), helicase (HEL) and RdRp domains, that are characteristic of all members of the alpha-like virus superfamily. 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.",