Studies of large and small scale virus capsid dynamics

描述（由申请方提供）：本提案阐述了与病毒颗粒成熟相关的大规模构象变化及其对颗粒稳定性和感染性的影响。生物组装是一个微妙的过程，需要亚基退火和自我校正的功能实体的形成。细胞内信号传导事件在此稳定性水平下充分启动，但病毒颗粒在其生命周期中具有需要稳健稳定性的细胞外和生物体外部分。颗粒成熟提供了一种机制，以适应适当组装（即原病毒）所需的弱相互作用，其中化学程序编码在原病毒中，导致成熟和稳定。我们将利用在支持的最后一个时期开发的系统来研究大规模构象变化及其驱动力的详细化学，稳定准等效衣壳相互作用的机制，自催化化学的激活和感染性的发生。所选择的古细菌、细菌和真核病毒系统生动地说明了这一过程的趋同进化，其中显著不同的途径实现了非常相似的最终结果。我们的工作已经导致了新的应用，电子冷冻显微镜和图像重建（CryoEM）研究，在体外，时间分辨形成的自催化活性位点在真核病毒成熟，亚纳米不对称重建的细菌病毒及其成熟中间体，并在体内成熟的古细菌病毒相关的人腺病毒。我们在下一个支持期间的重点将是使用近原子分辨率cryoEM来绘制具有内膜的病毒的原衣壳和成熟颗粒的结构，使用电子冷冻断层扫描和最大似然重建来辨别近对称衣壳中功能重要的不对称特征，以及使用氢/氘交换来增加真核病毒成熟中间体中亚基化学相互作用的分辨率。这项工作的结果将确定病毒成熟过程中的脆弱转变，并提供对大规模构象变化的基本见解，包括其生物物理驱动力和化学。

DESCRIPTION (provided by applicant): This proposal addresses large-scale conformational changes associated with virus particle maturation and their effect on particle stability and infectivity. Biological assembly is a delicate process requiring subunit annealing and self-correction in the formation of the functional entity. Intracellular signaling events are adequately initiated with this level of stability, but virus particles have an extra-cellular and extra-organism portion of their life cycle that requires robust stability. Particle maturation provides a mechanism to accommodate weak interactions required for proper assembly (i.e. the provirion) with a chemical program, encoded in the provirion, that leads to maturation and stability. We will utilize systems developed during the last period of support to investigate the detailed chemistry of large scale conformational changes and their driving forces, the mechanisms of stabilizing quasi-equivalent capsid interactions, the activation of auto-catalytic chemistry and the onset of infectivity. The archeal, bacterial and eukaryotic virus systems chosen vividly illustrate the convergent evolution of this process with dramatically different pathways achieving closely similar final results. Our work has lead to novel applications of electron cryo-microscopy and image reconstruction (CryoEM) to study, in vitro, time resolved formation of auto-catalytic active sites during eukaryotic virus maturation, sub-nanometer asymmetric reconstructions of bacterial viruses and their maturation intermediates, and in vivo maturation of an archaeal virus related to the human adenovirus. Our focus during the next period of support will be the use of near-atomic resolution cryoEM to map the structures of the procapsid and mature particles of a virus that has an internal membrane, to use of electron cryo-tomography and maximum likelihood reconstructions to discern functionally important asymmetric features in near symmetric capsids, and to use hydrogen/deuterium exchange to increase the resolution of subunit chemical interactions in maturation intermediates of a eukaryotic virus. The results of this effort will identify vulnerable transitions during virus maturation and provide fundamental insights into large-scale conformational changes including their biophysical driving forces and chemistry.