Structural and Functional Analyses of Toxin-Antitoxin Protein Complexes From Bact

Bact 毒素-抗毒素蛋白复合物的结构和功能分析

• 批准号: 8283468
• 负责人: Celia Goulding
• 金额: $ 20.74万
• 依托单位: UNIVERSITY OF CALIFORNIA-IRVINE
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-01 至 2014-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8283468
• 关键词: Affinity; Antitoxins; Bacteria; Binding; Biochemical; C-terminal; Calorimetry; Cell surface; Cells; Cleaved cell; Complex; Cytoplasm; Development; Ecology; Environment; Escherichia coli; Evolution; Exhibits; Gram-Negative Bacteria; Growth; Human; Immunity; Lead; Mediating; Membrane Proteins; Pathogenesis; Property; Proteins; Research; Resolution; Roentgen Rays; Sequence Homology; Structure; System; Toxin; antimicrobial; base; combat; in vivo; insight; novel; nuclease; pathogen; protein complex; protein protein interaction; stoichiometry

DESCRIPTION (provided by applicant): Bacteria have evolved complex strategies to compete and communicate in their environments. A new mechanism of inter-bacterial competition, termed contact- dependent growth inhibition (CDI) was recently discovered in Escherichia coli. CDI systems are found in a wide variety of gram-negative bacteria, including several important human pathogens. CDI is mediated by the CdiB/CdiA two-partner secretion system. CdiB is a predicted outer membrane protein that is required for the export and assembly of the CdiA exoprotein onto the cell surface. The C-terminal domain of CdiA (CdiA-CT) contains the growth inhibition activity and is presumably cleaved and translocated into the target cell cytoplasm to inhibit growth. CDI systems also encode CdiI immunity proteins, which bind and inactivate CdiA-CT toxins, thereby protecting CDI+ cells from autoinhibition. Remarkably, the CdiA-CT domain is polymorphic, with well over 60 different toxin sequences identified to date. Accordingly, the corresponding CdiI proteins are also highly variable. This sequence diversity suggests that CDI systems deploy a wide variety of toxic activities. Indeed, we have discovered that CdiA- CT domains exhibit a number of distinct nuclease activities. Because CdiI immunity proteins are specific for their cognate CdiA-CTs, the interactions underlying each toxin- immunity complex are presumably unique. There is currently no structural information available for any CdiA-CT/CdiI complex, and therefore the details of these protein- protein interactions are completely unknown. Moreover, the mechanisms by which CdiI proteins neutralize CdiA-CT activities are not understood. We propose structural and functional analyses to gain insights into the intricate toxin-immunity network encoded by bacterial CDI systems, which represents a unique opportunity to elucidate how specific binding is maintained as toxin-immunity pairs diverge through evolution. PUBLIC HEALTH RELEVANCE: Bacteria have evolved complex strategies to compete and communicate in their environments. A new mechanism of inter-bacterial competition, termed contact-dependent growth inhibition (CDI) has recently been discovered in a wide variety of gram-negative bacterial pathogens. This proposal utilizes a structure/function analysis to gain mechanistic insights into the intricate toxin-immunity protein network encoded by CDI systems. This research will have a significant impact on our understanding of bacterial pathogenesis and ecology and could lead to the development of novel antimicrobial therapies.

描述（由申请人提供）：细菌已经进化出复杂的策略来在其环境中竞争和交流。最近在大肠杆菌中发现了一种新的细菌间竞争机制，称为接触依赖性生长抑制（CDI）。 CDI 系统存在于多种革兰氏阴性细菌中，包括几种重要的人类病原体。 CDI 由 CdiB/CdiA 两方分泌系统介导。 CdiB 是一种预测的外膜蛋白，是 CdiA 外蛋白输出和组装到细胞表面所需的。 CdiA (CdiA-CT) 的 C 末端结构域含有生长抑制活性，可能被切割并易位到靶细胞的细胞质中以抑制生长。 CDI 系统还编码 CdiI 免疫蛋白，该蛋白结合并灭活 CdiA-CT 毒素，从而保护 CDI+ 细胞免受自身抑制。值得注意的是，CdiA-CT 结构域具有多态性，迄今为止已鉴定出 60 多种不同的毒素序列。因此，相应的 CdiI 蛋白也是高度可变的。这种序列多样性表明 CDI 系统具有多种毒性活性。事实上，我们发现 CdiA-CT 结构域表现出许多不同的核酸酶活性。由于 CdiI 免疫蛋白对其同源 CdiA-CT 具有特异性，因此每个毒素-免疫复合物背后的相互作用可能是独特的。目前没有任何 CdiA-CT/CdiI 复合物的结构信息，因此这些蛋白质-蛋白质相互作用的细节完全未知。此外，CdiI 蛋白中和 CdiA-CT 活性的机制尚不清楚。我们提出结构和功能分析，以深入了解细菌 CDI 系统编码的复杂毒素-免疫网络，这提供了一个独特的机会来阐明随着毒素-免疫对在进化过程中的分化，如何维持特异性结合。 公共卫生相关性：细菌已经进化出复杂的策略来在其环境中竞争和交流。最近在多种革兰氏阴性细菌病原体中发现了一种新的细菌间竞争机制，称为接触依赖性生长抑制（CDI）。该提案利用结构/功能分析来深入了解 CDI 系统编码的复杂毒素免疫蛋白网络。这项研究将对我们对细菌发病机制和生态学的理解产生重大影响，并可能导致新型抗菌疗法的发展。