Nidovirales
The order Nidovirales includes four families of viruses with a non- segmented, single-stranded RNA genome of positive polarity. The name derives from the Latin nidus ( nest ), which alludes to the nested ( engl. nested ) messenger RNAs of Nidovirales. The three families of the Nidovirales differ with respect to the structure and function of the viral replicase ( RNA polymerase) from all other RNA viruses. Due to structural studies of these replicases you first spoke of a " coronavirus -like superfamily " This is the reason a summary otherwise not made of other families in an order. The representatives of the Nidovirales cause important infections in mammals (especially the subfamily Coronavirinae ). Only the family Roniviridae is only found in shellfish.
Genome
The Nidovirales comparatively large RNA genomes of 13-16 kb ( Arterivirus ) up to 28-31 kb ( Coronaviridae ). In this subfamily is also that virus with the known non- segmented RNA genome biggest, the mouse hepatitis virus ( MHV ) with a size of 31 526 nt. The genomic RNA of the Nidovirales is polyadenylated and having (except for the genus Okavirus ) a cap structure at its 5 'end. Typically, the strategy of Nidovirales in the transcription of viral mRNAs. However, the different transcripts of at least one reading frame have the same polyA end different starting points, therefore they are polycistronic (nested ) mRNAs.
Taxonomy
- Order Nidovirales
- Family Coronaviridae
- Subfamily Coronavirinae
- Subfamily Toronavirinae
- Family Arteriviridae
- Genus arterivirus
- Family Roniviridae
- Genus Okavirus
- Family Mesoniviridae
- Genus Alphamesonivirus