VIRION
Non-enveloped, spherical virion about 26 nm in diameter with T=3 icosahedral symmetry composed of 178 CP proteins 889 dimers) and a single A2 maturation protein
.
GENOME
Monopartite, linear, ssRNA(+) genome about 4 kb in size. The 5' end is a triphosphate. Encodes 4 proteins.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. Encodes for 4 ORFs. Cp protein repress replicase translation by binding a RNA hairpin at the start site of this gene. Lysis protein is expressed by suppression of termination of an UGA nonsense codon in levivirus genus (readthrough).
ENZYMES
REPLICATION
- Adsorption to F pili of target cells induces cleavage and release of the maturation protein.
- Genomic RNA enters the bacterium.
- Viral proteins are translated.
- Viral replicase assembles with host proteins (ribosomal protein S1, translation elongation factors EF-Tu and EF-Ts) to form the active RNA polymerase.
- Replication of genomic RNA into a minus strand, which serves as template to produce new positive strand genomes.
- Late in infection CP protein bind to a RNA hairpin on the genome, and new virus particles are assembled in the cytoplasm.
- Release by cell lysis.