Department of Pathology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, UPM Serdang, Selangor, Malaysia.
CRUK Beatson Institute, Garscube Campus, Glasgow, Scotland United Kingdom.
PLoS Biol. 2018 Oct 22;16(10):e3000038. doi: 10.1371/journal.pbio.3000038. eCollection 2018 Oct.
Macrobrachium rosenbergii nodavirus (MrNV) is a pathogen of freshwater prawns that poses a threat to food security and causes significant economic losses in the aquaculture industries of many developing nations. A detailed understanding of the MrNV virion structure will inform the development of strategies to control outbreaks. The MrNV capsid has also been engineered to display heterologous antigens, and thus knowledge of its atomic resolution structure will benefit efforts to develop tools based on this platform. Here, we present an atomic-resolution model of the MrNV capsid protein (CP), calculated by cryogenic electron microscopy (cryoEM) of MrNV virus-like particles (VLPs) produced in insect cells, and three-dimensional (3D) image reconstruction at 3.3 Å resolution. CryoEM of MrNV virions purified from infected freshwater prawn post-larvae yielded a 6.6 Å resolution structure, confirming the biological relevance of the VLP structure. Our data revealed that unlike other known nodavirus structures, which have been shown to assemble capsids having trimeric spikes, MrNV assembles a T = 3 capsid with dimeric spikes. We also found a number of surprising similarities between the MrNV capsid structure and that of the Tombusviridae: 1) an extensive network of N-terminal arms (NTAs) lines the capsid interior, forming long-range interactions to lace together asymmetric units; 2) the capsid shell is stabilised by 3 pairs of Ca2+ ions in each asymmetric unit; 3) the protruding spike domain exhibits a very similar fold to that seen in the spikes of the tombusviruses. These structural similarities raise questions concerning the taxonomic classification of MrNV.
罗氏沼虾诺达病毒（MrNV）是一种淡水虾病原体，对许多发展中国家的水产养殖业的食品安全构成威胁，并造成重大经济损失。详细了解 MrNV 病毒粒子的结构将为制定控制疫情的策略提供信息。MrNV 衣壳也被设计用于展示异源抗原，因此了解其原子分辨率结构将有助于开发基于该平台的工具。在这里，我们通过冷冻电子显微镜（cryoEM）对在昆虫细胞中产生的 MrNV 病毒样颗粒（VLPs）进行成像，计算出 MrNV 衣壳蛋白（CP）的原子分辨率模型，并对其进行了三维（3D）图像重建，分辨率为 3.3Å。对从感染的罗氏沼虾幼体中纯化的 MrNV 病毒粒子进行 cryoEM 成像，得到了 6.6Å分辨率的结构，证实了 VLPs 结构的生物学相关性。我们的数据显示，与其他已知的组装有三聚体刺突的诺达病毒结构不同，MrNV 组装成具有二聚体刺突的 T=3 衣壳。我们还发现 MrNV 衣壳结构与 T ombusviridae 的一些惊人相似之处：1）大量的 N 端臂（NTAs）网络排列在衣壳内部，形成长程相互作用，将不对称单元连接在一起；2）每个不对称单元中的 3 对 Ca 2+离子稳定衣壳壳；3）突出的刺突结构域表现出与 T ombusviridae 刺突非常相似的折叠。这些结构上的相似性引发了关于 MrNV 分类学分类的问题。
