catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the Mesoniviridae family of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the catalytic core domain of RdRp of RNA viruses belonging to the family Mesoniviridae, order Nidovirales. Member viruses have a viral envelope and (+)ssRNA genome. The family is named after the size of the genomes relative to other nidoviruses, which is intermediate between that of the families Arteriviridae and Coronaviridae, with meso- coming from the Greek word mesos, which means medium, while -ni is an abbreviation of nido. The family Mesoniviridae comprises of mosquito-specific viruses with extensive geographic distribution and host range. The family has only one subfamily, Hexponivirinae, which contains only one genus, Alphamesonivirus. There are 8 subgenera (Casualivirus, Enselivirus, Hanalivirus, Kadilivirus, Karsalivirus, Menolivirus, Namcalivirus, and Ofalivirus) and 10 species in Alphamesonivirus. The structure of Mesoniviridae 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",