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

项目概要/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 称为核糖核苷酸还原酶（RNR）。几种已知的 RNR 类型，已分为 I、II 和 III 类的不同之处在于它们用来引发其反应的过渡金属和自由基化学 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 使用与人类 I 类 a 亚类明显不同的 I 类 RNR 来感染人类并导致疾病 酶。其中一些微生物 RNR（b 和 d 亚类）在以下情况中使用锰代替铁： 被认为是对人类免疫反应引起的缺铁的适应，而其他人则同时使用这两种方法 金属（c 类）。我们刚刚从链球菌性咽喉炎的病原体中发现了一种新型 RNR 通过使用以前的方法，猩红热可能已经完全摆脱了对过渡金属的通常依赖。 未知类型的稳定氨基酸残基，因此建立了 e 亚类。该项目将准确揭示如何 最近在 I 类 RNR 中发现的三个新亚类（包括 d 和 e）的成员 病原菌获得催化活性并引发核苷酸还原。截然不同的启蒙 病原体酶所使用的化学物质为抗生素选择性抑制提供了机会。这个 该项目将为此类药物发现工作提供概念基础，并将阐明方法 其中病原微生物已适应应对宿主的敌对免疫反应。

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.