Early steps in reovirus infection are associated with dramatic changes in supramolecular structure and protein conformation: analysis of virions and subviral particles by cryoelectron microscopy and image reconstruction.
Early steps in reovirus infection are associated with dramatic changes in supramolecular structure and protein conformation: analysis of virions and subviral particles by cryoelectron microscopy and image reconstruction.
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DOI：
10.1083/jcb.122.5.1023
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发表时间：
1993-09
影响因子：
7.8
通讯作者：
Baker, T S
中科院分区：
文献类型：
--
作者：
Dryden, K A;Wang, G;Yeager, M;Nibert, M L;Coombs, K M;Furlong, D B;Fields, B N;Baker, T S
1型Lang呼肠孤病毒的三种结构形式（病毒体、中间亚病毒颗粒[ISVP]和核心）已通过冷冻电子显微镜（cryoEM）和27至32-A分辨率的图像重建进行了检查。分析的三维地图和已知的生化组成允许确定衣壳蛋白的位置，球状形状，化学计量，四级组织，和与相邻的衣壳蛋白的相互作用。病毒粒子，ISVP和核心结构的比较和差异图的检查揭示了与呼肠孤病毒感染的早期步骤相关的超分子结构和蛋白质构象的巨大变化。完整的病毒粒子（直径约850-A）被设计用于环境稳定性，其中dsRNA基因组不仅受到外衣壳中紧密的σ 3-μ 1、λ 2-σ 3和λ 2-μ 1相互作用的保护，而且受到主要由λ 1和σ 2形成的密集包装的核壳的保护。分段的基因组似乎以液晶方式在半径< 240 A处包装。取决于病毒生长条件，病毒体经历肠蛋白酶或内体/溶酶体蛋白酶的切割，以产生活化的ISVP（直径约800-A）。这种转变涉及跨越半径从360到427 A的外部衣壳层的释放，所述外部衣壳层由σ 3的椭圆体亚基的60个四聚体和60个六聚体簇形成。顶点相关的细胞附着蛋白，西格玛1，也经历了一个惊人的变化，从一个不太可视化，更紧凑的形式，延长，灵活的纤维。这种构象变化可以使sigma 1与细胞表面受体的相互作用最大化。病毒mRNA的转录由核心颗粒（直径约600-A）介导，核心颗粒由ISVP在穿透和脱壳后产生。从ISVP到核心的转变涉及释放12 σ 1纤维和剩余的由200个跨越半径从306到395 A的棒状μ 1亚基的三聚体形成的外部衣壳层。在病毒体和ISVP中，λ 2蛋白的花形五聚体集中在顶点.在ISVP到核心的过渡中，λ 2亚基的结构域旋转并向上和向外摆动，以形成从半径305 A延伸到400 A的塔状结构，其直径为184 A，并且中心通道宽为84 A。这种新的构象变化允许潜在的扩散底物的转录和退出新合成的mRNA片段。（400字处删节）
Three structural forms of type 1 Lang reovirus (virions, intermediate subviral particles [ISVPs], and cores) have been examined by cryoelectron microscopy (cryoEM) and image reconstruction at 27 to 32-A resolution. Analysis of the three-dimensional maps and known biochemical composition allows determination of capsid protein location, globular shape, stoichiometry, quaternary organization, and interactions with adjacent capsid proteins. Comparisons of the virion, ISVP and core structures and examination of difference maps reveal dramatic changes in supra-molecular structure and protein conformation that are related to the early steps of reovirus infection. The intact virion (approximately 850-A diam) is designed for environmental stability in which the dsRNA genome is protected not only by tight sigma 3-mu 1, lambda 2-sigma 3, and lambda 2-mu 1 interactions in the outer capsid but also by a densely packed core shell formed primarily by lambda 1 and sigma 2. The segmented genome appears to be packed in a liquid crystalline fashion at radii < 240 A. Depending on viral growth conditions, virions undergo cleavage by enteric or endosomal/lysosomal proteases, to generate the activated ISVP (approximately 800-A diam). This transition involves the release of an outer capsid layer spanning radii from 360 to 427 A that is formed by 60 tetrameric and 60 hexameric clusters of ellipsoidal subunits of sigma 3. The vertex- associated cell attachment protein, sigma 1, also undergoes a striking change from a poorly visualized, more compact form, to an extended, flexible fiber. This conformational change may maximize interactions of sigma 1 with cell surface receptors. Transcription of viral mRNAs is mediated by the core particle (approximately 600-A diam), generated from the ISVP after penetration and uncoating. The transition from ISVP to core involves release of the 12 sigma 1 fibers and the remaining outer capsid layer formed by 200 trimers of rod-shaped mu 1 subunits that span radii from 306 to 395 A. In the virion and ISVP, flower- shaped pentamers of the lambda 2 protein are centered at the vertices. In the ISVP-to-core transition, domains of the lambda 2 subunits rotate and swing upward and outward to form a turret-like structure extending from radii 305 to 400 A, with a diameter of 184 A, and a central channel 84 A wide. This novel conformational change allows the potential diffusion of substrates for transcription and exit of newly synthesized mRNA segments.(ABSTRACT TRUNCATED AT 400 WORDS)