Is the HIV-1 capsid modulated by a pentamer switch?

项目概要/摘要 HIV-1CA蛋白的12个五聚体具有塑造富勒烯锥几何形状的关键功能 在成熟的衣壳中，通过占据六角形衣壳晶格中的下倾或尖锐的曲率点， 从而允许组装的蛋白质壳闭合。除了这一结构性作用， 以前被归因于CA五聚体。在这里，我们提出了一个新的功能作用的艾滋病毒-1 CA 五聚体。我们的前提是，有两个不同的构象状态的五聚体，一个最初 通过体外组装系统鉴定，第二个观察到平均五聚体构型 在病毒体中。已发表的研究和我们的初步数据表明，这两种五聚体形式的区别在于： 两个配体结合位点的构型：一个为IP6，另一个为苯丙氨酸-甘氨酸（FG） 含有宿主蛋白如NUP153和其他核孔蛋白、CPSF6和SEC24C。我们建议 不同的五聚体状态定义了调节衣壳进入后结构的分子开关。我们 进一步提出，我们的五聚体开关假说可以解释理解不多的衣壳特性， 功能，如基础衣壳稳定性，脱壳和衣壳抑制的机制。在这 探索性R21项目，我们的主要目标是确定结构和生物化学性质的 提出了五聚体开关，并验证了构象转换与配体偶联的关键预测 约束力在两个特定目标中，我们将应用蛋白质热分析和cryoEM的现代实现， 在新的和建立的体外衣壳模型系统，范围从可溶性五聚体组装 captase样颗粒。如果得到证实，我们的新颖和创新的五聚体开关假设将大大扩展 了解HIV-1衣壳功能的分子基础，并可以为开发新的 靶向抗病毒药物

Project Summary/Abstract Twelve pentamers of the HIV-1 CA protein have the critical function of shaping the fullerene cone geometry of the mature capsid, by occupying declinations or sharp points of curvature in the hexagonal capsid lattice, and thereby allowing the assembling protein shell to close. Apart from this structural role, no other function has been previously ascribed to the CA pentamer. Here, we propose a novel functional role for the HIV-1 CA pentamer. Our premise is that there are two distinct conformational states of the pentamer, one initially identified through in vitro assembly systems and the second observed as the average pentamer configuration in virions. Published studies and our preliminary data indicate that the two pentamer forms are distinguished by the configurations of two ligand binding sites: one for IP6, and another for phenylalanine-glycine (FG) containing host proteins such as NUP153 and other nucleoporins, CPSF6 and SEC24C. We propose that the distinct pentamer states define a molecular switch that modulates the post-entry structure of the capsid. We further propose that our pentamer switch hypothesis can explain poorly-understood capsid properties and functions, such as mechanisms that underlie capsid stability, uncoating and capsid inhibition. In this exploratory R21 project, our major goals are to define the structural and biochemical properties of the proposed pentamer switch and test the key prediction that conformational switching is coupled to ligand binding. In two Specific Aims, we will apply modern implementations of protein thermal profiling and cryoEM, on novel and established in vitro capsid model systems that range from soluble pentamers to assembled capsid-like particles. If proven, our novel and innovative pentamer switch hypothesis would significantly expand understanding of the molecular basis of HIV-1 capsid function and could inform the development of novel capsid-targeted antivirals.