Notes on Genus: Avibirnavirus
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| icosahedra |
Type member: Infectious bursal disease virus
Contents
| Members of this Genus General Description Morphology Electron Micrograph Genome Genus Genomic Organization Genome Map Type Member Genomic Organization Curated Sequences |
General Description
The genus Avibirnavirus (from the Latin avis = bird) is one of four genera in the family Birnaviridae and contains viruses isolated from birds.Morphology
Virions isometric (icosahedral), not enveloped, 60 nm in diameter, made of 260 units trimeric subunits.Genome
Bipartite double-stranded RNA of about 3.2 and 2.8 kb, each with a genome-linked protein (VPg) at the 5'-terminus and no 3'-polyA tail.Genus Genomic Organization
Each segment encodes a large polyprotein that it is subsequently processed into the functional products and there is an additional, smaller ORF on the larger (A) segment. The two capsid proteins and a non-structural protein are encoded on segment A and an RNA-dependent RNA polymerase on segment B.Type Member Genomic Organization
Segment A (3.2 kb) encodes:- ORF1: 16-17 kDa, non-structural protein VP5 of unknown function
- ORF2: 106-110 kDa, Polyprotein that is subsequently processed into:
- VP2, major outer capsid protein precursor that undergoes further truncation and cleavage
- VP4, protease
- VP3, internal capsid protein