Structure of Nora virus at 2.7 Å resolution and implications for receptor binding, capsid stability and taxonomy

DOI: 10.1038/s41598-020-76613-1

Authors: Pasi Laurinmaki (University of Helsinki) , Shabih Shakeel (MRC Laboratory of Molecular Biology; University of Helsinki) , Jens-Ola Ekström (Umeå University; University of Tampere) , Pezhman Mohammadi (University of Helsinki) , Dan Hultmark (Umeå University; University of Tampere) , Sarah J. Butcher (University of Helsinki)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Scientific Reports , VOL 10

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 14263

Abstract: Nora virus, a virus of Drosophila, encapsidates one of the largest single-stranded RNA virus genomes known. Its taxonomic affinity is uncertain as it has a picornavirus-like cassette of enzymes for virus replication, but the capsid structure was at the time for genome publication unknown. By solving the structure of the virus, and through sequence comparison, we clear up this taxonomic ambiguity in the invertebrate RNA virosphere. Despite the lack of detectable similarity in the amino acid sequences, the 2.7 Å resolution cryoEM map showed Nora virus to have T = 1 symmetry with the characteristic capsid protein β-barrels found in all the viruses in the Picornavirales order. Strikingly, α-helical bundles formed from the extended C-termini of capsid protein VP4B and VP4C protrude from the capsid surface. They are similar to signalling molecule folds and implicated in virus entry. Unlike other viruses of Picornavirales, no intra-pentamer stabilizing annulus was seen, instead the intra-pentamer stability comes from the interaction of VP4C and VP4B N-termini. Finally, intertwining of the N-termini of two-fold symmetry-related VP4A capsid proteins and RNA, provides inter-pentamer stability. Based on its distinct structural elements and the genetic distance to other picorna-like viruses we propose that Nora virus, and a small group of related viruses, should have its own family within the order Picornavirales.

Journal Keywords: Evolution; Genetics; Microbiology; Molecular biology; Structural biology; Viral proteins; Virus structures

Diamond Keywords: Viruses

Subject Areas: Biology and Bio-materials

Diamond Offline Facilities: Electron Bio-Imaging Centre (eBIC)
Instruments: Krios I-Titan Krios I at Diamond

Added On: 18/11/2020 14:17

Documents:
s41598-020-76613-1.pdf

Discipline Tags:

Pathogens Infectious Diseases Health & Wellbeing Genetics Structural biology Life Sciences & Biotech

Technical Tags:

Microscopy Electron Microscopy (EM) Cryo Electron Microscopy (Cryo EM)