Notes on Genus: Okavirus
Type member: Gill-associated virus
This is currently the only genus in the family Roniviridae
doviruses) and is named after the crustacean lymphoid organ (oka) in which the viruses are commonly found.
Virions enveloped and bacilliform, 150-200 nm x 40-60 nm.
Monopartite positive sense single-stranded RNA of size about 26kb and with a 3'-polyA tail.
Genus Genomic Organization
Two large, overlapping ORFs at the 5'-end of the genome encode the major non-structural proteins and are expressed as a fusion protein by ribosomal frameshift. Downstream are about 4 other genes, encoding structural proteins, and these are expressed from a 3'-coterminal nested set of subgenomic RNAs.
Type Member Genomic Organization
The RNA of 26.2kb is translated into the following products:
- Replication protein 1a of 460 kDa
- Polymerase 1b of 302 kDa expressed as a fusion protein with 1a by ribosomal frameshift
- Coat protein ORF2 of 16 kDa
- Structural protein precursor ORF3 of 182 kDa processed into two glycoproteins (gp116 and gp64) and a putative transmembrane protein of 25 kDa
- Putative ORF4 of 9 kDa