The crystal structure of cricket paralysis virus: the first view of a new virus family.

Numerous small, RNA-containing insect viruses are currently classified as picornaviruses, or as 'picorna-like', since they superficially resemble the true picornaviruses. Considerable evidence now suggests that several of these viruses are members of a distinct family. We have determined the gene sequence of the capsid proteins and the 2.4 A resolution crystal structure of the cricket paralysis virus. While the genome sequence indicates that the insect picorna-like viruses represent a distinct lineage compared to true picornaviruses, the capsid structure demonstrates that the two groups are related. These viral genomes are, thus, best viewed as composed of exchangeable modules that have recombined.