Molecular mechanisms of antibacterial CDI toxin activation

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序列变化很大，有60个不同的序列 细菌基因组中识别的毒素/免疫蛋白家族。我们最近发现几个CDI 毒素/免疫蛋白与其他细胞蛋白形成高阶复合体。我们假设这些 细胞蛋白作为“允许”因子激活目标细菌内的CDI毒素。分子 CDI毒素激活的机制以及更广泛的生理意义尚不清楚。 毒素/允许因子复合体。这项应用提出了遗传、生化和 生物物理方法，以获得对支配蛋白质-蛋白质相互作用网络的机械性洞察 CDI公司。这项研究将大大增加我们对细菌生态和进化的理解 病原体，并可为抗菌治疗的新战略提供信息。

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 >60 distinct toxin/immunity protein families recognized in bacterial genomes. We recently discovered that several CDI toxin/immunity proteins form higher order complexes with other cellular proteins. We hypothesize that these cellular protein function as "permissive" factors to activate CDI toxins inside target bacteria. The molecular mechanisms of CDI toxin activation are poorly understood, as are the broader physiological implications of toxin/permissive factor complexes. This application proposes 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.