Bacterial Microcompartment Cargo Packing and Ultrastructure: High-Resolution Studies of Native Alpha-Carboxysomes

项目摘要/摘要 细菌缺乏细胞器，但一些酶途径产生的中间产物要么是容易感染的 如果释放到细胞质中，可能会对细胞产生毒性。大约20%的细菌包裹着潜在的 细菌微室(BMC)内这些途径的危险或低效成分。宝马拥有 在许多物种中具有特征，并具有从固碳到小分子的各种作用 新陈代谢。它们通常含有两种或两种以上的酶、数量可变的附件和支架 蛋白质，以及一个致密的蛋白质壳，不需要脂质的帮助，它可以选择性地渗透到小分子 薄膜。壳蛋白和壳层的异质组成在所有的骨髓细胞中都是保守的。 到目前为止所描述的所有功能中。因为BMCs可以让细菌生活在恶劣的环境中，它们 对人类健康、生态和传染病有广泛的影响。宝马也成为了 蛋白质工程由于其潜在的包裹货物的选择替代药物和 生物技术应用，以及它们作为许多物种的关键组成部分的基本价值 新陈代谢。尽管它们很重要，但结构的异质性阻碍了对 壳蛋白和货物的结构、超微结构和空间组织。这项研究 这里提出的旨在描述羧基体的结构和组织的特征，这是一个负责的BMC模型 用来固定蓝藻中的碳。高分辨率冷冻电子断层扫描和亚断层图像平均将 用于测定体外和体内的货物组织和外壳的超微结构，保存和 描述了这些结构的保守的非均质性。除了提供对BMC的新见解之外 生物学及其保守的复杂性，这项研究还将产生新的可应用的分析方法 许多复杂的BMC和病毒系统。

Project Summary/Abstract Bacteria lack organelles, yet some enzymatic pathways generate intermediates which are either susceptible to loss or which could be toxic to the cell if released into the cytosol. Roughly 20% of bacteria encase the potentially dangerous or inefficient components of these pathways inside bacterial microcompartments (BMCs). BMCs have been characterized in a number of species, and serve a variety of roles from carbon fixation to small molecule metabolism. They typically contain two or more enzymes, a variable number of accessory and scaffolding proteins, and a compact protein shell that is selectively permeable to small molecules without the aid of a lipid membrane. The shell proteins and the heterogeneous composition of the shell are conserved across all BMCs of all functions characterized thus far. Because BMCs can allow bacteria to live in hostile environments, they have broad implications for human health, ecology and infectious disease. BMCs have also become a target of protein engineering due to their potential for enclosing cargos of choice for alternative pharmacological and biotechnological applications, as well as for their basic value as a critical component of many species’ metabolism. Despite their importance, structural heterogeneity has prevented a complete understanding of architecture, ultrastructure, and spatial organization of both the shell proteins and the cargo. The research proposed here seeks to characterize the structure and organization of carboxysomes, a model BMC responsible for carbon fixation in cyanobacteria. High-resolution cryo-electron tomography and sub-tomogram averaging will be used to determine cargo organization and shell ultrastructure in vitro and in vivo, preserving and characterizing the conserved heterogeneity of the structures. In addition to providing new insights into BMC biology and its conserved complexity, this research will also generate new analysis methods that can be applied to many complicated BMC and viral systems.