Chemistry and Biology of Bacterial Sulfonucleotide Reductases

硫代谢途径对人类病原体的毒力和生存至关重要。在微生物中 半胱氨酸生物合成、硫代核苷酸还原酶(SRS)催化5‘-磷酸-硫代腺苷还原 (APS)或3‘-磷酸-5’-磷酸-5‘-硫代腺苷(PAPS)从蛋白质中还原为亚硫酸盐 辅因子硫氧还蛋白(Trx)。在后期，亚硫酸盐被进一步还原为硫化物，用于生产 基本的含硫代谢物，包括半胱氨酸、蛋氨酸、辅酶、铁硫簇和 抗氧化剂。SRs是开发抗生素的极佳新靶点，因为它们在细菌中起着关键作用 人类的生存和缺乏类似的酶。这类酶特别耐人寻味，因为 它们催化的化学反应的性质。此外，我们的初步结果表明， APS还原酶中异常的铁-硫簇可能起着重要的催化作用。然而，许多基本的 关于它们的机制和结构的问题仍然未知。因为它的化学和生物学 细菌的SRS还没有被很好地理解，科学家们还没有能够探索这些酶的潜力 作为抗感染的目标。为此，该项目的广泛目标是获得详细的 细菌SRS的机制和结构信息，以及识别SRS的小分子抑制剂。 提出的研究有三个具体目的：(1)阐明[4Fe-4S]簇在APS中的作用 还原酶，(2)研究SR催化循环中的大尺度构象动力学，以及(3) 使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 开发可用于对抗耐药细菌的抗生素，这将有一个主要的 对人类健康的影响。此外，我们预计这些实验将带来重要的新的 对蛋白质相关铁硫簇和细菌硫的(生物)化学的基本认识 新陈代谢。

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.