Chemistry and Biology of Bacterial Sulfonucleotide Reductases

描述（由申请人提供）：硫代谢途径对人类病原体的毒力和生存至关重要。在微生物半胱氨酸生物合成中，磺核苷酸还原酶（SRs）利用蛋白质辅助因子硫氧还蛋白（Trx）的还原等效物催化5'-磷酸磺基腺苷（APS）或3‘-磷酸-5’磷酸磺基腺苷（PAPS）还原为亚硫酸盐。在后期阶段，亚硫酸盐进一步还原为硫化物，用于生产必需的含硫代谢物，包括半胱氨酸、蛋氨酸、辅酶、铁硫簇和抗氧化剂。由于SRs在细菌存活和人类缺乏类似酶中起着关键作用，因此它是抗生素开发的优秀新靶点。由于它们催化的化学反应的性质，这类酶特别有趣。此外，我们的初步结果表明，APS还原酶中极不寻常的铁硫簇可能起重要的催化作用。然而，关于它们的机制和结构的许多基本问题仍不清楚。由于对细菌SRs的化学和生物学还不太了解，科学家们还无法探索这些酶作为抗感染靶点的潜力。为此，该项目的总体目标是获得细菌SRs的详细机制和结构信息，并确定SRs的小分子抑制剂。本研究有三个具体目的：(1)阐明[4Fe-4S]簇在APS还原酶中的功能；(2)研究SR催化循环中的大规模构象动力学；(3)利用文库筛选和虚拟对接方法发现SR抑制剂。这项工作可能会导致抗生素的发展，可用于对抗耐药细菌，这将对人类健康产生重大影响。此外，我们预计这些实验将为蛋白质相关铁硫簇和细菌硫代谢的（生物）化学提供重要的新基础见解。公共卫生相关性：细菌必须从其环境中吸收硫酸盐才能生存并引发人类感染。发现阻止这一过程的方法可能对公共卫生产生深远影响。全球迫切需要新的抗微生物疗法；通过阻断硫酸盐代谢干扰细菌毒力的能力代表了一种全新的治疗方法，在临床上是及时的。

DESCRIPTION (provided by applicant): Sulfur metabolic pathways are essential for the virulence and survival of human pathogens. In microbial cysteine biosynthesis, sulfonucleotide reductases (SRs) catalyze the reduction of 5'-phosphosulfoadenosine (APS) or 3'-phospho-5'phosphosulfoadenosine (PAPS) to sulfite using reducing equivalents from a protein cofactor, thioredoxin (Trx). In later stages, sulfite is further reduced to sulfide, which is used for the production of essential sulfur-containing metabolites including cysteine, methionine, coenzymes, iron-sulfur clusters and antioxidants. SRs are excellent new targets for antibiotic development because of their critical role in bacterial survival and the lack of analogous enzymes in humans. This class of enzymes is particularly intriguing due to the nature of the chemical reaction they catalyze. In addition, our preliminary results suggest that a highly unusual iron-sulfur cluster in APS reductase may play an important catalytic role. However, many fundamental questions about their mechanism and structure remain unknown. Because the chemistry and biology of bacterial SRs is not well understood, scientists have not been able to explore the potential of these enzymes as anti-infective targets. To this end, the broad goal of this project is directed towards obtaining detailed mechanistic and structural information on bacterial SRs, and on identifying small molecule inhibitors of SRs. The proposed research has three Specific Aims: (1) To elucidate the function of the [4Fe-4S] cluster in APS reductase, (2) To investigate large-scale conformational dynamics in the SR catalytic cycle, and (3) To discover SR inhibitors using library screening and virtual docking approaches. This work may lead to the development of antibiotics that can be used to combat drug-resistant bacteria, which would have a major impact on human health. Furthermore, we anticipate that these experiments will lead to important new fundamental insights into the (bio)chemistry of protein-associated iron-sulfur clusters and bacterial sulfur metabolism. PUBLIC HEALTH RELEVANCE: Bacterial must assimilate sulfate from their environment in order to survive and initiate human infections. The discovery of methods to block this process could have a profound impact of public health. There is an urgent, global need for new antimicrobial therapies; the ability to interfere with bacterial virulence by intercepting sulfate metabolism represents a completely new therapeutic approach and is clinically timely.