Backbone structure of the infectious ε15 virus capsid revealed by electron cryomicroscopy
Backbone structure of the infectious ε15 virus capsid revealed by electron cryomicroscopy
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DOI：
10.1038/nature06665
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发表时间：
2008-02-28
期刊：
影响因子：
64.8
通讯作者：
Chiu, Wah
中科院分区：
文献类型：
--
作者：
Jiang, Wen;Baker, Matthew L.;Chiu, Wah
在确定蛋白质的第一个三维晶体结构 (1) 半个世纪后，已经报道了从单一多肽到大型组装体的 40,000 多种结构 (2)。然而，晶体学家面临的挑战仍然是衍射晶体的生长。在这里，我们通过单粒子电子冷冻显微镜报告了 22-MDa 大分子组装体的 4.5 埃分辨率结构，即传染性 epsilon15 (epsilon 15) 粒子的衣壳。根据该密度图，我们构建了其主要衣壳蛋白、基因产物 7 (gp7) 的完整主链轨迹。即使没有可检测到的序列相似性，该结构也揭示了与其他有尾双链 DNA 病毒相似的蛋白质结构 (3,4)。然而，gp7 中二级结构元素（拓扑）的连通性是独特的。在两倍轴周围观察到突出的密度，但 gp7 无法解释这一点。随后对整个病毒进行的蛋白质组学分析将这些密度鉴定为 gp10，一种 12 kDa 的蛋白质。其结构、位置和与衣壳的高结合亲和力表明 gp10 二聚体充当相邻衣壳之间的分子主食，以确保颗粒的稳定性。除了 epsilon 15 之外，该方法还可能提供一种新方法，用于模拟其他大分子组装体中接近天然溶液状态的蛋白质亚基的骨架构象。
A half- century after the determination of the first three-dimensional crystal structure of a protein(1), more than 40,000 structures ranging from single polypeptides to large assemblies have been reported(2). The challenge for crystallographers, however, remains the growing of a diffracting crystal. Here we report the 4.5- angstrom resolution structure of a 22-MDa macromolecular assembly, the capsid of the infectious epsilon15 ( epsilon 15) particle, by single-particle electron cryomicroscopy. From this density map we constructed a complete backbone trace of its major capsid protein, gene product 7 ( gp7). The structure reveals a similar protein architecture to that of other tailed double- stranded DNA viruses, even in the absence of detectable sequence similarity(3,4). However, the connectivity of the secondary structure elements ( topology) in gp7 is unique. Protruding densities are observed around the two- fold axes that cannot be accounted for by gp7. A subsequent proteomic analysis of the whole virus identifies these densities as gp10, a 12- kDa protein. Its structure, location and high binding affinity to the capsid indicate that the gp10 dimer functions as a molecular staple between neighbouring capsomeres to ensure the particle's stability. Beyond epsilon 15, this method potentially offers a new approach for modelling the backbone conformations of the protein subunits in other macromolecular assemblies at near- native solution states.