Notes on Genus: Sapovirus
Type member: Sapporo virus
This is one of the genera in the family Calicviridae
. In common with members of the genera Lagovirus
, the coat protein is at the C-terminus of the polyprotein but the genera have different host specificities and are distinct in phylogenetic analyses.
Virions isometric (icosahedral), not enveloped, 35-40 nm in diameter, made of 90 dimers of the coat protein. There are 32 cup-shaped depressions at each of the fivefold and threefold axes.
Monopartite positive sense single-stranded RNA c.
7.4 kb in length with a genome-linked protein (VPg) at the 5'-terminus and a 3'-polyA tail.
Genus Genomic Organization
The RNA encodes a polyprotein that has (from N- to C- termini) helicase, VPg, protease, polymerase and coat protein domains. There are one or perhaps two additional, smaller, ORFs.
Type Member Genomic Organization
The genome of about 7,400 nucleotides is translated into:
- Polyprotein of 251.3 kDa, which is proteolytically processed into 7 or more mature proteins including (in order from N- to C- termini) helicase, VPg, protease, polymerase and coat protein
- Possible ORF (17.5 kDa) nested within the polyprotein
- ORF2 of 17.8 kDa that may be a minor structural component of the virion