Function of novel antibacterial toxins

项目摘要 细菌已经进化出复杂的策略来相互竞争和交流。一 细菌间竞争重要机制是接触依赖性生长抑制（CDI）。CDI系统 在多种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家族的双伴侣分泌蛋白介导。CdiB是Omp 85外膜 CdiA胞外蛋白是将CdiA胞外蛋白输出和组装到细胞表面所需的蛋白。CdiA结合至 受体，然后将其C末端毒素结构域（CdiA-CT）递送到靶细胞中。 这些系统还编码CdiI免疫蛋白，其特异性结合CdiA-CT并中和毒素 保护CDI+细胞免受自抑制的活性。CdiA-CT/CdiI序列高度可变，>130 细菌基因组中识别的不同毒素/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货物可以被运送到目标细菌的细胞质中。本申请 试图确定分子和结构基础，使这种显着的功能可塑性。 我们将使用遗传学、生物化学和生物物理学方法的组合来获得对以下方面的机械见解： 控制CDI的蛋白质-蛋白质相互作用网络。这项研究将大大提高我们的 了解细菌病原体的生态学和进化，并可以为新的战略提供信息， 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.