Notes on Genus: Kobuvirus


Type member: Aichivirus A


General Description

The genus Kobuvirus (from the Japanese kobu = hump or knob, reflecting the distinctive icosahedral structure of this group of viruses) is one of the genera in the family Picornaviridae. Genome organisation is fairly conserved within the family but members of this genus have a 5'-UTR without a polyC tract, and a leader protease. There is no internal capsid (1A) 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.


Monopartite positive sense single-stranded RNA c. 8.3 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 near the N-terminus.

Type Member Genomic Organization

The genome of about 8,300 nucleotides is translated into a single polyprotein, which is subsequently processed into eleven products:
L 19.4 kDaLeader protease
1B  39.1 kDaCoat protein VP2 (surface capsid protein)
1C 24.2 kDaCoat protein VP3 (surface capsid protein)
1D 29.9 kDaCoat protein VP1 (surface capsid protein)
2A 11.7 kDanon-structural protein, possibly a protease
2B 17.5 kDanon-structural protein
2C 37.1 kDanon-structural protein
3A 10.7 kDanon-structural protein
3B 3.1 kDaGenome-linked protein (VPg)
3C 20.5 kDaprotease
3D 52.5 kDapolymerase