Notes on Genus: Mamastrovirus
Type member: Human astrovirus
This is the one of two genera in the family Astroviridae
. It consists of viruses that infect mammals some of whose virions have a star-shaped appearance (Greek astron
Virions isometric (icosahedral), not enveloped, 28-30 nm in diameter, 10% of which have a distinctive 5- or 6-pointed star shape.
Monopartite positive sense single-stranded RNA 6.8-7.9 kb in length with a 3'-polyA tail.
Genus Genomic Organization
The non-structural proteins are encoded by two ORFs that are expressed as one by ribosomal frameshift. The coat protein precursor is towards the 3'-end of the genome and is translated from a subgenomic RNA.
Type Member Genomic Organization
The genome of about 6,800 nucleotides has three open reading frames:
- Replication protein 1a (105 kDa)
- Polymerase 1b expressed as a fusion protein of 164 kDa with 1a
- Coat protein precursor of 86 kDa that is subsequently processed into two or three proteins