Notes on Genus: Cosavirus
icosahedra
Type member: Cosavirus A
Contents
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.
Morphology
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.
Genome
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 kDa | Coat protein VP4 (internal capsid protein) |
| 1B |
29.2 kDa | Coat protein VP2 (surface capsid protein) |
| 1C |
25.8 kDa | Coat protein VP3 (surface capsid protein) |
| 1D |
32.4 kDa | Coat protein VP1 (surface capsid protein) |
| 2A |
3.2 kDa | non-structural protein |
| 2B |
13.6 kDa | non-structural protein |
| 2C |
35.6 kDa | non-structural protein |
| 3A |
12.2 kDa | non-structural protein |
| 3B |
2.2 kDa |
Genome-linked protein (VPg) |
| 3C |
22.5 kDa | protease |
| 3D |
52.4 kDa | polymerase |
