Notes on Genus: Mamastrovirus

icosahedra
icosahedra

Type member: Human astrovirus

Contents

General Description

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 = star).

Morphology

Virions isometric (icosahedral), not enveloped, 28-30 nm in diameter, 10% of which have a distinctive 5- or 6-pointed star shape.

Genome

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