catalytic core domain of RNA-dependent RNA polymerase (RdRp) in the family Solemoviridae of positive-sense single-stranded RNA [(+)ssRNA] viruses
This group contains the RdRp of RNA viruses belonging to the family Solemoviridae, order Sobelivirales. Plant viruses in the family Solemoviridae have stable icosahedral particles assembled on T=3 symmetry and a relatively small (4-4.6 kb) monopartite (+)ssRNA genome with 4-5 open reading frames (ORFs). The natural host range is relatively narrow for each virus. Viral transmission occurs via mechanical wounding, by vegetative propagation or abiotically through soil; insects (beetles, aphids, thrips, hoppers, mirid bugs, moths) can also be vectors. Viruses infecting legumes or plants from the family Chenopodiaceae may be seed-transmissible. Members of the family are classified into four genera: Sobemovirus, Polemovirus, Polerovirus, Enamovirus. The viral polyprotein contains domains of the membrane anchor, a serine protease, a genome-linked viral protein (VPg) and C-terminal protein(s) or an RdRp, expressed by means of ribosomal frameshifting. 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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