Role of a novel auto-protease domain in antibacterial toxin delivery

项目总结 接触依赖生长抑制(CDI)是细菌间竞争的重要机制 广泛存在于各种革兰氏阴性菌中，包括许多重要的人类病原体。CDI是 由CDIB/CDIA家族的两个伙伴分泌蛋白介导，它们被认为是以二元组的形式组装的 细胞表面的复合体。CDIA形成一条细丝，从与抑制物细胞结合的地方伸出 敏感细菌上的受体。结合受体后，CDIA递送其C末端毒素结构域(CDIA-CT) 进入目标单元格。CDI系统还编码CDI免疫蛋白，与CDIA-CT特异性结合 并中和毒素活性，以保护细胞免受自身抑制。CDIA-CT/CDI序列非常适合 可变的，与细菌基因组中识别的130种不同的毒素/免疫蛋白序列类型。CDIA-CT 毒素是模块化的，可以在CDIA蛋白之间交换以产生功能嵌合体。这些 观察表明，许多不同种类的有毒物质可以被输送到目标的细胞质中 细菌。这项申请寻求确定实现这一点的分子和结构基础 显著的功能可塑性。我们将使用分子遗传、生化和结构的组合 深入了解CDIA组成结构域之间的功能相互作用的方法。这 研究将显著增加我们对CDIA功能的机械理解，并可能为小说 抗菌治疗的策略。

Project summary Contact-dependent growth inhibition (CDI) is an important mechanism of inter-bacterial competition found in a wide variety of Gram-negative bacteria, including many important human pathogens. CDI is mediated by the CdiB/CdiA family of two-partner secretion proteins, which are thought to assemble as a binary complex on the cell surface. CdiA forms a thin filament to projects away from the inhibitor cell to bind to receptors on susceptible bacteria. After binding receptor, CdiA delivers its C-terminal toxin domain (CdiA-CT) into the target cell. CDI systems also encode CdiI immunity proteins, which specifically bind to the CdiA-CT and neutralize toxin activity to protect the cell from auto-inhibition. CdiA-CT/CdiI sequences are extraordinarily variable, with >130 distinct toxin/immunity protein sequence types recognized in bacterial genomes. CdiA-CT toxins are modular and can be exchanged between CdiA proteins to generate functional chimeras. These observations indicate that many different kinds of toxic cargo can be delivered into the cytoplasm of target bacteria. This application seeks to determine the molecular and structural underpinnings that enable this remarkable functional plasticity. We will use a combination of molecular genetic, biochemical and structural approaches to gain insight into the functional interactions between the constituent domains of CdiA. This research will significantly increase our mechanistic understanding of CdiA function and could inform novel strategies for antimicrobial therapy.