Notes on Genus: Orthoreovirus


Type member: Mammalian orthoreovirus


General Description

This is one of the animal virus genera in the family Reoviridae. Members have 10 segments, particles more than 70 nm in diameter and sedimentation coefficients greater than 600S.


Virions isometric (icosahedral), c.85 nm in diameter, with a double capsid shell surrounding a core of c.48 nm. Core particles have distinctive turrets at the fivefold axes.


Linear, double stranded RNA in 10 segments. Each virion contains a single copy of the entire genome. Total genome up to c.24000 nucleotides long.

Genus Genomic Organization

Most segments have a single ORF. The segments are usually labelled as large (L1-3), medium (M1-3) or small (S1-4) with reference to their mobility in electrophoresis.

Type Member Genomic Organization

  • Segment 1 (L1) (3854 nt) encodes the minor core RNA polymerase protein lambda-3 of 142.3 kDa
  • Segment 2 (L2) (3915 nt) encodes the core spike protein lambda-2 of 143.9 kDa
  • Segment 3 (L3) (3901 nt) encodes the major core protein lambda-1 of 141.9 kDa
  • Segment 4 (M1) (2304 nt) encodes a protein (mu-2) of 83.3 kDa
  • Segment 5 (M2) (2203 nt) encodes the outer core protein precursor mu-1 of 76.3 kDa
  • Segment 6 (M3) (2241 nt) encodes the non-structural protein mu-NS of 80.2 kDa
  • Segment 7 (S1) (1462 nt) encodes the minor capsid cell attachment protein sigma-1a of 45.5 kDa and a non-structural protein (sigma-ibNS) of 14.0 kDa
  • Segment 8 (S2) (1331 nt) encodes a protein (sigma-2) of 37.7 kDa
  • Segment 9 (S3) (1198 nt) encodes a non-structural RNA binding protein (sigma-NS) of 41.2 kDa
  • Segment 10 (S4) (1196 nt) encodes the major capsid protein sigma-3 of 41.1 kDa