Notes on Family: Caliciviridae
This family consists of viruses that infect vertebrates and which have isometric virions (35-40 nm) and a monopartite ssRNA genome which encodes a polyprotein and one or two smaller ORFs. It is of interest to plant virologists because there are some similarities to the picornavirus "'superfamily"", including the plant virus families Sequiviridae
. The name is from the Latin calix
(= cup) because of the distinctive cup-shaped depressions in the virion surface.
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 7.4-8.3 kb in length with a genome-linked protein (VPg) at the 5'-terminus and a 3'-polyA tail. It encodes a polyprotein that has helicase, VPg, protease and polymerase domains. In some genera, the coat protein is at the C-terminus of the polyprotein, while in others it is encoded by a separate ORF. There is usually an additional small ORF encoding a basic protein of unknown function.
Genera in the Family
- Lagovirus (coat protein at C-terminus of polyprotein; infecting rabbits and hares)
- Nebovirus (coat protein at C-terminus of polyprotein; infecting cattle)
- Norovirus (coat protein translated from a separate ORF overlapping with the polyprotein)
- Sapovirus (coat protein at C-terminus of polyprotein; causing gastroenteritis in humans)
- Vesivirus (coat protein translated from a separate ORF following the polyprotein)