Diverse Transition-Metal and Free-Radical Chemistry Enabling 2'-Deoxyribonucleotide Production by Bacteria in Restrictive Environments

项目摘要/摘要 所有生物体都通过酶的作用获得DNA合成和修复的脱氧核苷酸底物 被称为核糖核苷酸还原酶(RNR)。已知的几种类型的RNR，分为 第一，第二和第三类，不同的是过渡金属和自由基化学，他们用来启动他们的 常见的、具有挑战性的还原/脱羟基反应。最近的研究表明，许多细菌 在人类中感染和引起疾病使用的第一类rnr与人类第一类、a亚类明显不同。 酵素。其中一些微生物RNR(b亚类和d亚类)使用锰而不是铁 被认为是对人类免疫反应引起的铁缺乏的一种适应，其他人两者都使用 金属(c亚类)。我们刚刚发现一种新型的RNR，来自链球菌性咽喉炎的病原体和 猩红热可能已经完全摆脱了对过渡金属的常见依赖，因为它使用了以前的 未知类型的稳定氨基酸自由基，从而建立了e亚类。这个项目将准确地揭示 最近于#年发现的三个新的I类RNRs亚类成员(包括d和e) 病原菌获得它们的催化活性，并启动核苷酸还原。完全不同的启蒙 病原体的酶所使用的化学物质为抗生素选择性地抑制它们提供了机会。这 该项目将为这种药物发现工作提供概念上的基础，并将阐明 其中病原微生物已经适应了它们的宿主的敌意免疫反应。

Project Summary/Abstract All organisms obtain the deoxynucleotide substrates for DNA synthesis and repair by the action of an enzyme known as ribonucleotide reductase (RNR). The several known types of RNRs, which have been divided into classes I, II, and III, differ in the transition-metal and free-radical chemistry that they use to initiate their common, challenging reduction/dehydroxylation reaction. Recent studies have shown that many bacteria that infect and cause disease in humans use class I RNRs that differ markedly from the human class I, subclass a enzyme. Some of these microbial RNRs (subclasses b and d) use manganese instead of iron in what is thought to be an adaptation to iron deprivation caused by the human immune response, and others use both metals (subclass c). We just discovered that a new type of RNR from the causative agent of strep throat and scarlet fever may have fully escaped the usual dependence on transition metals by using a previously unknown type of stable amino acid radical, thus founding subclass e. This project will reveal precisely how the members of three new subclasses of class I RNRs (including d and e) that were recently identified in pathogenic bacteria acquire their catalytic activity and initiate nucleotide reduction. The very different initiation chemistry used by the pathogens' enzymes offers opportunities for their selective inhibition by antibiotics. This project will provide the conceptual underpinnings for such drug discovery efforts and will shed light on the ways in which pathogenic microbes have adapted to cope with their hosts' hostile immune response.