Notes on Genus: Betacoronavirus

enveloped spheres

Type member: Murine coronavirus

Contents

Members of this Genus
General Description
Morphology
Electron Micrograph
Genome
Genus Genomic Organization
Genome Map
Type Member Genomic Organization
Curated Sequences

General Description

This is one of the genera in the subfamily Coronavirinae of the family Coronaviridae. Within this subfamily, viruses have spherical virions with club-shaped surface projections and a core shell. The name is from the Latin corona = crown, reflecting the appearance of these projections in electron microscopy. This genus contains what were previously considered phylogroup 2 coronaviruses.

Morphology

Virions enveloped and spherical 120-160 nm in diameter, with a core shell of about 65nm. The large surface projections are formed by glycoproteins and a trimers of the spike protein.

Genome

Monopartite positive sense single-stranded RNA 29-31 kb in length 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. These contain regions with protease, helicase and RNA polymerase motifs. Downstream are up to 9 other genes, most of which encode structural proteins, and these are expressed from a 3'-coterminal nested set of subgenomic RNAs. The major characterised proteins occur in a conserved order and are:

Type Member Genomic Organization

The RNA of 31.3kb is translated into the following products: