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: 8416307
• 负责人: Celia Goulding
• 金额: $ 17.27万
• 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 2015-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8416307
• 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.

描述（由申请人提供）：细菌已经发展了复杂的策略，以在其环境中进行竞争和交流。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两伴侣分泌系统介导。 CDIB是一种预测的外膜蛋白，它是CDIA ofrototein在细胞表面的导出和组装所必需的。 CDIA（CDIA-CT）的C末端结构域包含生长抑制活性，并且可能被裂解并转移到靶细胞质中以抑制生长。 CDI系统还编码结合和失活CDIA-CT毒素的CDII免疫蛋白，从而保护CDI+细胞免受自抑制。值得注意的是，CDIA-CT结构域是多态性的，迄今为止，鉴定出60多个不同的毒素序列。因此，相应的CDII蛋白也是高度可变的。该序列多样性表明CDI系统部署了各种有毒活动。确实，我们发现CDIACT结构域表现出许多不同的核酸酶活性。由于CDII免疫蛋白针对其同源CDIA-CTS具有特异性，因此每个毒素免疫复合物的相互作用可能是独一无二的。目前尚无任何CDIA-CT/CDII复合物可用的结构信息，因此这些蛋白质相互作用的细节是完全未知的。此外，不了解CDII蛋白中和CDIA-CT活性的机制。我们提出了结构和功能分析，以了解由细菌CDI系统编码的复杂毒素免疫网络的见解，这代表了阐明如何维持特定结合的独特机会，因为毒素免疫配对通过进化而散布。