Cheng Lingpeng, Fang Qin, Shah Sanket, Atanasov Ivo C, Zhou Z Hong
Department of Microbiology, Immunology and Molecular Genetics, The University of California at Los Angeles, CA 90095-7364, USA.
J Mol Biol. 2008 Sep 26;382(1):213-22. doi: 10.1016/j.jmb.2008.06.075. Epub 2008 Jul 3.
Grass carp reovirus (GCRV) is a member of the Aquareovirus genus of the family Reoviridae, a large family of double-stranded RNA (dsRNA) viruses infecting plants, insects, fishes and mammals. We report the first subnanometer-resolution three-dimensional structures of both GCRV core and virion by cryoelectron microscopy. These structures have allowed the delineation of interactions among the over 1000 molecules in this enormous macromolecular machine and a detailed comparison with other dsRNA viruses at the secondary-structure level. The GCRV core structure shows that the inner proteins have strong structural similarities with those of orthoreoviruses even at the level of secondary-structure elements, indicating that the structures involved in viral dsRNA interaction and transcription are highly conserved. In contrast, the level of similarity in structures decreases in the proteins situated in the outer layers of the virion. The proteins involved in host recognition and attachment exhibit the least similarities to other members of Reoviridae. Furthermore, in GCRV, the RNA-translocating turrets are in an open state and lack a counterpart for the sigma1 protein situated on top of the close turrets observed in mammalian orthoreovirus. Interestingly, the distribution and the organization of GCRV core proteins resemble those of the cytoplasmic polyhedrosis virus, a cypovirus and the structurally simplest member of the Reoviridae family. Our results suggest that GCRV occupies a unique structure niche between the simpler cypoviruses and the considerably more complex mammalian orthoreovirus, thus providing an important model for understanding the structural and functional conservation and diversity of this enormous family of dsRNA viruses.
草鱼呼肠孤病毒（GCRV）是呼肠孤病毒科水生呼肠孤病毒属的成员，呼肠孤病毒科是一个庞大的双链RNA（dsRNA）病毒家族，可感染植物、昆虫、鱼类和哺乳动物。我们通过冷冻电子显微镜首次报道了GCRV核心颗粒和病毒粒子的亚纳米分辨率三维结构。这些结构使我们能够描绘出这个巨大的大分子机器中1000多个分子之间的相互作用，并在二级结构水平上与其他dsRNA病毒进行详细比较。GCRV核心结构表明，即使在二级结构元件水平上，其内部蛋白与正呼肠孤病毒的内部蛋白也有很强的结构相似性，这表明参与病毒dsRNA相互作用和转录的结构高度保守。相比之下，病毒粒子外层蛋白的结构相似性水平降低。参与宿主识别和附着的蛋白与呼肠孤病毒科其他成员的相似性最低。此外，在GCRV中，RNA转运炮塔处于开放状态，并且在哺乳动物正呼肠孤病毒中观察到的位于封闭炮塔顶部的sigma1蛋白没有对应物。有趣的是，GCRV核心蛋白的分布和组织类似于细胞质多角体病毒，一种质型多角体病毒，也是呼肠孤病毒科结构最简单的成员。我们的结果表明，GCRV在较简单的质型多角体病毒和复杂得多的哺乳动物正呼肠孤病毒之间占据独特的结构位置，从而为理解这个庞大的dsRNA病毒家族的结构和功能保守性及多样性提供了一个重要模型。
