Notes on Genus: Cosavirus


Type member: Cosavirus A


General Description

The genus Cosavirus (common stool-associated virus) is one of the genera in the family Picornaviridae. Genome organisation is fairly conserved within the family but members of this genus have a large 5'-UTR, no leader protease and a single, very small, 2A protein.


Virions isometric (icosahedral), not enveloped 30 nm in diameter, made of 60 units (protomers) each consisting of one molecule of each of three surface coat proteins and with a fourth internal capsid protein.


Monopartite positive sense single-stranded RNA 7.6 kb in length. There is a genome-linked protein (VPg) at the 5'-terminus and a 3'-polyA tail.

Genus Genomic Organization

The RNA encodes a single polyprotein that is subsequently processed into the functional products. The major structural proteins are encoded at the N-terminus.

Type Member Genomic Organization

The genome of about 7,600 nucleotides is translated into a single polyprotein, which is subsequently processed into eleven products:
1A   6.8 kDaCoat protein VP4 (internal capsid protein)
1B   29.2 kDaCoat protein VP2 (surface capsid protein)
1C 25.8 kDaCoat protein VP3 (surface capsid protein)
1D 32.4 kDaCoat protein VP1 (surface capsid protein)
2A 3.2 kDanon-structural protein
2B 13.6 kDanon-structural protein
2C 35.6 kDanon-structural protein
3A 12.2 kDanon-structural protein
3B 2.2 kDa Genome-linked protein (VPg)
3C 22.5 kDaprotease
3D 52.4 kDapolymerase