Crystallization and X-ray diffraction of virus-like particles from a piscine betanodavirus

Abstract

Dragon grouper nervous necrosis virus (DGNNV), a member of the genusBetanodavirus, causes high mortality of larvae and juveniles of the grouper fishEpinephelus lanceolatus. Currently, there is no reported crystal structure of a fish nodavirus. The DGNNV virion capsid is derived from a single open reading frame that encodes a 338-amino-acid protein of approximately 37 kDa. The capsid protein of DGNNV was expressed to form virus-like particles (VLPs) inEscherichia coli. The VLP shape isT= 3 quasi-symmetric with a diameter of ∼38 nm in cryo-electron microscopy images and is highly similar to the native virion. In this report, crystals of DGNNV VLPs were grown to a size of 0.27 mm within two weeks by the hanging-drop vapour-diffusion method at 283 K and diffracted X-rays to ∼7.5 Å resolution. In-house X-ray diffraction data of the DGNNV VLP crystals showed that the crystals belonged to space groupR32, with unit-cell parametersa=b= 353.00,c= 800.40 Å, α = β = 90, γ = 120°. 23 268 unique reflections were acquired with an overallRmergeof 18.2% and a completeness of 93.2%. Self-rotation function maps confirmed the fivefold, threefold and twofold symmetries of the icosahedron of DGNNV VLPs.