Assembly and Dynamics of Bacterial Chemosensory Signaling Arrays

近60年来，趋化性（chemotaxis）——一种普遍存在的使细胞或生物体向或远离化学物质运动的生物行为——已经成为研究细胞感觉信号转导和运动行为的典范模型。大肠杆菌相对简单的趋化机制是最容易理解的生物信号转导系统，是研究蛋白质用于检测、处理和传递刺激信息的分子机制的有力工具。大肠杆菌细胞通过一种感觉装置对化学环境的变化做出反应，这种感觉装置是由数百个基本核心信号单元组成的有序阵列（化学感觉阵列），由三种基本成分组成：检测环境的跨膜化学感受器、将信号传递给下游效应器的组氨酸激酶和接头蛋白。核心单元进一步组装成二维晶格阵列，允许细胞放大和整合许多不同的和可能相互冲突的信号，以确定最佳的生长条件。在细菌性病原体中，趋化反应对定植和感染至关重要。因此，介导这种反应的信号转导系统是抗菌药物开发的潜在新靶点。为了理解化学传感阵列组装、激活和高协同性的潜在分子机制，有必要确定核心信号组件之间的精确相互作用，在阵列的背景下，以及它的动态特性。在本项目中，我们建议结合尖端的低温电镜结构方法、计算建模和多尺度分子模拟，以及体内功能分析进行结构验证，研究化学感觉阵列信号转导和调节的结构和动力学机制。我们的研究结果将在原子细节上建立个体信号如何在受体之间传递、自适应调节，并随后在多个受体蛋白上整合以共同影响激酶活性，突出合作蛋白信号的一般特征。不同趋化物种所采用的分子机制的显著重叠将极大地扩展我们的结果的相关性，包括广泛的人类和植物病原体中的信号转导。

For nearly six decades, chemotaxis - a ubiquitous biological behavior enabling the movement of a cell or organism toward or away from chemicals -has severed as a paradigmatic model for the study of cellular sensory signal transduction and motile behavior. The relatively simple chemotaxis machinery of the bacterium Escherichia coli is the best understood biological signal transduction system and serves as a powerful tool for investigating the molecular mechanisms that proteins use to detect, process, and transmit stimulus information. E. coli cells respond to changes in their chemical environment through a sensory apparatus that is an ordered array (chemosensory array) of hundreds of basic core signalling units consisting of three essential components, the transmembrane chemoreceptors that detects the environment, the histidine kinase that passes the signal to the downstream effector, and the adaptor protein. The core units further assemble into a two-dimensional lattice array which allows cells to amplify and integrate many varied and possibly conflicting signals to locate optimal growing conditions. In bacterial pathogens, chemotaxis response is crucial for colonization and infection. Thus, the signal transduction systems that mediate such responses are potential new targets for antimicrobial drug development. To understand the underlying molecular mechanisms of chemosensory array assembly, activation and high cooperativity, it is essential to determine the precise interactions between the core signalling components, in the context of the array, and its dynamical properties. In this project, we propose to use a combination of cutting-edge cryoEM structural methods and computational modeling and multi-scale molecular simulations, as well as in vivo functional assays for structural validation, to investigate the structural and dynamical mechanisms underlying signal transduction and regulation in the chemosensory array. Our results will establish, in atomistic detail, how individual signals are transmitted across the receptor, adaptively regulated, and subsequently integrated over multiple receptor proteins to jointly affect kinase activity, highlighting general features of cooperative protein signaling. The significant overlap in molecular machinery employed by diverse chemotactic species will greatly extend the relevance of our results, including to signal transduction within a wide-range of human and plant pathogens.