Coordination Chemistry of Microbial Iron Transport Compounds

描述（由申请人提供）：美国每年报告近50万例细菌性脓毒症病例，其中约三分之一的病例是致命的。铁是微生物生长中的限制性营养素;细菌主要通过产生铁载体、具有高铁亲和力和选择性的低分子量螯合剂来获得铁。铁的可用性在确定入侵病原体的毒力方面是必不可少的。最成功的人类病原体，如炭疽杆菌，设计了精心设计的多方面策略来确保其铁供应。该项目旨在了解铁载体运输系统：1）从结构水平，研究铁结合的热力学和动力学，2）到系统水平，在这些铁载体的识别和运输到细菌中之后，3）到环境水平，探索环境如何，例如温度，宿主免疫系统，其他细菌的存在，甚至暴露于光，影响细菌的生长。我们的实验室配备了独特的设备来进行这一系列的研究，并追求以下具体目标：1。了解铁载体的结构与功能之间的关系。2.研究革兰氏阳性菌铁载体介导的铁转运。3.探讨微生物铁转运的铁载体穿梭机制的范围和功能。4.进一步描述人类免疫系统蛋白（铁载体）识别铁载体的机制，以及这种免疫反应的选择性如何被最危险的细菌病原体利用。为了满足这些目标，铁载体的功能，如热力学稳定性和铁载体铁络合物的还原电位，它们的铁结合动力学和亲脂性，将被确定为目标铁载体，并通过构建合成的铁载体类似物和配位类似物，我们将探索铁载体功能。几乎所有关于细菌铁载体介导的铁转运的已知信息都存在于革兰氏阴性细菌中;革兰氏阳性细菌现在是我们的目标，因为这组生物体包括许多重要的人类病原体。我们已经合作确定芽孢杆菌属物种的膜相关蛋白受体的晶体结构，这将补充我们在这个家族中的研究。我们的第一份报告的铁载体穿梭机制表明，两个铁载体之间的金属交换是必不可少的铁运输的革兰氏阴性细菌的研究。我们计划看看这种机制在细菌属中的分布有多广泛;我们现在提出了一种扩展的实验方法，该方法采用同位素标记的天然铁载体。我们最近开始了解我们所谓的“铁载体隐形”：逃避铁载体的结构修饰的铁结合。通过使用合成类似物和细菌铁载体分离物，以及标记的底物和突变蛋白，我们打算描述的选择性和生理过程的siderocalin。公共卫生相关性：在美国，每年报告近50万例细菌性败血症，其中约三分之一是致命的。铁是微生物生长中的限制性营养素;细菌主要通过产生铁载体、具有高铁亲和力和选择性的低分子量螯合剂来获得铁。这个项目确定了这个过程是如何发生的，以及人类免疫系统如何对抗它。

DESCRIPTION (provided by applicant): Nearly half a million cases of bacterial sepses are reported annually in the USA and approximately one third of the cases are fatal. Iron is a limiting nutrient in microbial growth; bacteria primarily obtain iron through production of siderophores, low molecular weight chelating agents with high ferric affinity and selectivity. The availability of iron is essential in determining the virulence of an invading pathogen. The most successful human pathogens, such as Bacillus anthracis, devise elaborate, multifaceted strategies to ensure their iron supply. This project seeks to understand siderophore transport systems: 1) from a structural level, studying the thermodynamics and kinetics of iron binding, 2) to a systemic level, following the recognition and transport of these siderophores into the bacteria, 3) to an environmental level, exploring how the surroundings, such as temperature, host immune system, presence of other bacteria and even exposure to light, affect the growth of the bacteria. We are uniquely equipped in our laboratory to carry out this range of studies and to pursue the following specific aims: 1. To understand the relationship between structure and function of siderophores. 2. To characterize siderophore-mediated iron transport in Gram-positive bacteria. 3. To explore the scope and functioning of the siderophore shuttle mechanism of microbial iron transport. 4. To further describe the mechanism of recognition of siderophores by proteins of the human immune system (siderocalin) and how the selectivity of this immune response is exploited by the most dangerous bacterial pathogens. To meet these Aims siderophore features such as thermodynamic stability and reduction potential of siderophore ferric complex, their kinetics of iron binding, and lipophilicity, will be determined for targeted siderophores and through the construction of synthetic siderophore analogs and coordination analogs we will explore siderophore function. Almost everything that is known about bacterial siderophore-mediated iron transport is in Gram-negative bacteria; Gram-positive bacteria are now our target, since this group of organisms includes many important human pathogens. We have in place collaborations to determine the crystallographic structures of membrane-associated protein receptors of Bacillus species that will complement our studies in this family. Our first report of the siderophore shuttle mechanism showed that metal exchange between two siderophores was essential for iron transport in the Gram-negative bacteria studied. We plan to see how widely distributed is this mechanism is among genera of bacteria; we now propose an extended experimental approach that incorporates the use of isotopically labeled natural siderophores. We have recently begun to develop an understanding of what we call "siderophore stealth": the evasion of siderocalin binding by structural modification of the siderophore. Through the use of synthetic analogs and bacterial siderophore isolates, as well as labeled substrates and mutant proteins, we intend to describe the selectivity and physiological course of siderocalin. PUBLIC HEALTH RELEVANCE: Nearly half a million cases of bacterial sepses are reported annually in the USA and approximately one third of the cases are fatal. Iron is a limiting nutrient in microbial growth; bacteria primarily obtain iron through production of siderophores, low molecular weight chelating agents with high ferric affinity and selectivity. This project determines how this process occurs and how the human immune system counters it.