Redox reactions in the biosynthesis of thio-cofactors in bacteria

维生素和其他小分子被定义为化学结构中含有硫的辅因子，在自然界中广泛分布，对地球上的生命至关重要。所有已知的生物体在新陈代谢的各个方面至少使用这些辅因子的一个子集。虽然它们在维持基本生化反应中的重要性已被广泛认识，但硫的活化、运输和插入辅因子的机制仍不完全清楚。然而，人们普遍认为，游离氨基酸半胱氨酸是细菌、真核生物和某些古生物中大多数含硫辅因子生物合成的硫来源。一种名为半胱氨酸脱硫酶的酶家族催化硫活化的第一步。该项目将确定生理性还原剂--特别是硫氧还蛋白和含硫小分子(谷胱甘肽、杆菌硫醇和霉硫醇)--在生物合成反应中的作用，并确定控制半胱氨酸脱硫酶及其硫受体活性的特定蛋白质相互作用。该项目将扩大代表不足群体的参与，包括塞勒姆学院和吉尔福德学院的本科生研究人员。塞勒姆学院和吉尔福德学院是两个规模较小的地方机构，主要是本科院校。作为联合导师的研究生将在准备成为未来的独立教师-学者时获得更好的沟通技能。半胱氨酸脱硫酶催化的反应涉及过硫中间体的形成和转移到参与铁-S簇生物合成的受体分子、转录核糖核酸、核糖核酸和脱氧核糖核酸中的硫代核苷、生物素、硫辛酸、钼辅因子和硫胺素的合成。研究硫代辅因子生物合成中的硫转移反应是具有挑战性的。主要的挑战之一是硫磺受体蛋白经常在多个生物合成途径中共享。该项目将通过研究参与不同途径的不同半胱氨酸脱硫酶来确定生理还原剂在促进细菌中硫代辅因子生物合成中的氧化还原反应中的作用。这项研究的结果将提供关于氧化还原剂在涉及硫转移的生化途径中所起作用的基础知识，并将建立控制生物合成酶活性的进化决定因素。该项目由数学和物理科学局生物科学局分子和细胞生物科学司分子生物物理学专题组和数学和物理科学局化学司生命过程化学专题组联合支助。

Vitamins and other small molecules defined as cofactors that contain sulfur in their chemical structures are widely distributed in nature and essential for life on Earth. All known living organisms use at least a subset of these cofactors in various aspects of metabolism. While their importance in sustaining basic biochemical reactions is widely recognized, the mechanisms of sulfur activation, trafficking, and insertion into cofactors remain not fully understood. It is widely recognized, however, that the free amino acid cysteine is the source of sulfur for the biosynthesis of most sulfur-containing cofactors in bacteria, eukaryotes, and some species of archaea. A family of enzymes named cysteine desulfurases catalyze the first step in sulfur activation. This project will determine the effect of physiological reducing agents -specifically, thioredoxins and small molecules that contain sulfur (glutathione, bacillithiol, and mycothiol)- in biosynthetic reactions and identify specific protein interactions controlling the reactivity of cysteine desulfurases and their sulfur acceptors. This project will broaden the participation of underrepresented groups by including undergraduate researchers from Salem College and Guilford College, two smaller, local, primarily undergraduate institutions. Graduate students serving as co-mentors will gain improved communication skills in preparation as future independent teacher-scholars.The reaction catalyzed by cysteine desulfurases involves the formation and transfer of a persulfide intermediate to acceptor molecules involved in the biosynthesis of Fe-S clusters, thionucleosides in tRNA, rRNA and DNA, biotin, lipoic acid, molybdenum cofactor, and thiamine. Studying sulfur-transfer reactions in the biosynthesis of thio-cofactors is challenging. One of the major challenges is that sulfur-acceptor proteins are often shared across multiple biosynthetic pathways. This project will determine the involvement of physiological reductants in promoting redox reactions in the biosynthesis of thio-cofactors in bacteria by investigating different cysteine desulfurases that are involved in distinct pathways. The outcome of this study will provide fundamental knowledge regarding the role of redox agents in biochemical pathways involved in the transfer of sulfur and will establish evolutionary determinants controlling reactivity of biosynthetic enzymes. This project is supported jointly by the Molecular Biophysics Cluster of the Molecular and Cellular Biosciences Division in the Directorate for Biological Sciences and Chemistry for Life Processes Cluster of Chemistry Division in the Directorate for Mathematical and Physical Sciences.