Family: Pleolipoviridae

Genus: Alphapleolipovirus

Distinguishing features

In addition to the conserved cluster of genes found in all members of the family Pleolipoviridae, alphapleolipoviruses share two ORFs: one encoding a putative rolling circle replication initiation proteins (RCR Rep), and another one encoding a putative protein of unknown function (Figure 1. Pleolipoviridae, see Family description). In all alphapleolipoviruses, the latter ORF is located between the ORF for RCR Rep and the conserved cluster of pleolipoviral genes. Viruses of the genus Alphapleolipovirus contain either a circular double-stranded or single-stranded DNA genome (Pietilä et al., 2009, Roine et al., 2010, Senčilo et al., 2012, Li et al., 2014).

Virion

Morphology

The virion structure of HRPV-1 has been determined by cryo-electron microscopy and tomography (Pietilä et al., 2012). The virion contains a continuous, approximately 4.2 nm thick membrane, which includes the internal membrane protein VP3. The complexes of VP4 spikes protrude from the membrane surface in irregular arrays. The ~7 nm long complexes are anchored to the membrane by their C-terminal domains. The spike protein structures of HRPV-2 and HRPV-6 have been solved by X-ray crystallography and their V-shaped folds are unique and represent a new structural type of fusion proteins (El Omari et al., 2019).

Proteins

Virions contain two major structural proteins: an internal membrane protein (e.g. HRPV-1VP3 protein), and a spike protein (e.g. HRPV-1 VP4 protein). In addition, a minor structural protein VP8 has been identified in HRPV-1, which is predicted to be an NTPase.

Species demarcation criteria

Viruses with genomes that differ by more than 5% are assigned to different species.

See also the genus demarcation criteria at the family level