RICE DWARF VIRUS STRUCTURAL STUDIES

蓝舌病毒(BTV)(呼肠孤病毒科，环状病毒属)是一种 无包膜的二十面体双链RNA病毒。几种蛋白质 层层包裹着基因组。在单元格输入时，外层为 剥离后留下一个表面由VP7组成的核心。这个 用X射线确定了三聚体VP7分子的结构 结晶学。连接的VP7亚单位由两个结构域组成， 一个主要是α螺旋的，另一个是较小的结构域，带有 熟悉的“果冻卷”拓扑结构。它们的相对方位 两个结构域以不同的晶体形式变化。一张23分辨率的地图 使用电子冷冻显微镜(CryoEM)数据确定了核心， 揭示了260个VP7三聚体以相当精确的T=13来组织 二十面体晶格。VP7层占据260之间的外壳和 三百四十五从核心的中心开始。在此半径以下(230-260)谎言 由120个VP3分子组成的T=1层。通过拟合X射线结构 从单个VP7三聚体到CryoEM结构，我们有 生成了BTV的VP7层的原子模型并演示了 在孤立的晶体中看到的分子结构之一 VP7对应于核心分子的构象。这个 VP7的β桶结构域位于核心外部并与其相互作用 成熟病毒粒子外层的蛋白质。较低的 VP7的α螺旋结构域与VP3的内层相互作用。 T=13层中相邻的VP7三聚体主要通过 在更广泛的较低领域中定义明确的区域，并很好地符合 准等价理论所期望的结构，没有 单个三聚体内的显著构象变化。这个 VP3层决定了颗粒的大小，并形成了相当光滑的 VP7三聚体的二维晶格的底物 躺下了。

Bluetongue virus (BTV) (Reoviridae family, Orbivirus genus) is a non-enveloped, icosahedral double-stranded RNA virus. Several protein layers enclose the genome. Upon cell entry the outer layer is stripped away leaving a core whose surface is composed of VP7. The structure of the trimeric VP7 molecule has been determined using X-ray crystallography. The articulated VP7 subunit consists of two domains, one largely alpha-helical and the other a smaller domain with the familiar 'jelly-roll' topology. The relative orientations of these two domains vary in different crystal forms. A 23 resolution map of the core determined, using electron cryo microscopy (cryoEM) data, reveals 260 trimers of VP7 organized on a rather precise T=13 laevo icosahedral lattice. The VP7 layer occupies a shell between 260
and 345
from the center of the core. Below this radius (230-260
) lies the T=1 layer of 120 molecules of VP3. By fitting the X-ray structure of the individual VP7 trimer to the cryoEM structure, we have generated an atomic model of the VP7 layer of BTV and demonstrated that one of the molecular structures seen in crystals of the isolated VP7 corresponds to the conformation of the molecule in the core. The beta barrel domains of VP7 are external to the core and interact with the protein in the outer layer of the mature virion. The lower alpha-helical domains of VP7 interact with the inner layer of VP3. Adjacent VP7 trimers in the T=13 layer interact principally through well defined regions in the broader lower domains and conform well to the structure expected from the theory of quasi-equivalence, with no significant conformational changes within the individual trimers. The VP3 layer determines the particle size and forms a rather smooth substrate upon which the two dimensional lattice of VP7 trimers is laid down.