Function of novel antibacterial toxins

项目总结 细菌已经进化出复杂的策略来相互竞争和交流。一 细菌间竞争的重要机制是接触依赖生长抑制(CDI)。CDI系统 在各种各样的革兰氏阴性细菌中发现，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。CDIB是一种Omp85外膜 CDIA外源蛋白出口和组装到细胞表面所需的蛋白质。CDIA绑定到 然后将其C-末端毒素结构域(CDIA-CT)传递到靶细胞。 这些系统还编码CDI免疫蛋白，这些蛋白与CDIA-CT特异性结合并中和毒素 保护CDI细胞免受自身抑制的活性。CDIA-CT/CDI序列是高度可变的，具有&gt；130 细菌基因组中识别的独特的毒素/免疫蛋白序列类型。CDIA-CT毒素是模块化的 并且可以在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输送到目标细菌的细胞质中。此应用程序 试图确定使这种非凡的功能可塑性得以实现的分子和结构基础。 我们将结合使用遗传学、生物化学和生物物理学的方法来获得对 支配CDI的蛋白质-蛋白质相互作用网络。这项研究将显著增加我们的 了解细菌病原体的生态和进化，并可为制定新的战略提供参考 抗菌治疗。

Project summary Bacteria have evolved complex strategies to compete and communicate with one another. One important mechanism of inter-bacterial competition is contact-dependent growth inhibition (CDI). CDI systems are 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. CdiB is an Omp85 outer-membrane protein that is required for the export and assembly of the CdiA exoprotein onto the cell surface. CdiA binds to receptors on susceptible bacteria and then delivers its C-terminal toxin domain (CdiA-CT) into the target cell. These systems also encode CdiI immunity proteins, which specifically bind to the CdiA-CT and neutralize toxin activity to protect CDI+ cells from auto-inhibition. CdiA-CT/CdiI sequences are highly 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 genetic, biochemical and biophysical approaches to gain mechanistic insight into the network of protein-protein interactions that govern CDI. This research will significantly increase our understanding of the ecology and evolution of bacterial pathogens and could inform novel strategies for antimicrobial therapy.