The infectious particle of insect-borne totivirus-like Omono River virus has raised ridges and lacks fibre complexes.

Okamoto K, Miyazaki N, Larsson DS, Kobayashi D, Svenda M, Mühlig K, Maia FR, Gunn LH, Isawa H, Kobayashi M, Sawabe K, Murata K, Hajdu J

Sci Rep 6 (-) 33170 [2016-09-12; online 2016-09-12]

Omono River virus (OmRV) is a double-stranded RNA virus isolated from Culex mosquitos, and it belongs to a group of unassigned insect viruses that appear to be related to Totiviridae. This paper describes electron cryo-microscopy (cryoEM) structures for the intact OmRV virion to 8.9 Å resolution and the structure of the empty virus-like-particle, that lacks RNA, to 8.3 Å resolution. The icosahedral capsid contains 120-subunits and resembles another closely related arthropod-borne totivirus-like virus, the infectious myonecrosis virus (IMNV) from shrimps. Both viruses have an elevated plateau around their icosahedral 5-fold axes, surrounded by a deep canyon. Sequence and structural analysis suggests that this plateau region is mainly composed of the extended C-terminal region of the capsid proteins. In contrast to IMNV, the infectious form of OmRV lacks extensive fibre complexes at its 5-fold axes as directly confirmed by a contrast-enhancement technique, using Zernike phase-contrast cryo-EM. Instead, these fibre complexes are replaced by a short "plug" structure at the five-fold axes of OmRV. OmRV and IMNV have acquired an extracellular phase, and the structures at the five-fold axes may be significant in adaptation to cell-to-cell transmission in metazoan hosts.

Mass Spectrometry-based Proteomics, Uppsala [Service]

PubMed 27616740

DOI 10.1038/srep33170

Crossref 10.1038/srep33170

pii: srep33170
pmc: PMC5018817