Redox reactions in the biosynthesis of thio-cofactors in bacteria

维生素和其他被定义为辅助因子的小分子在其化学结构中含有硫，它们广泛分布在自然界中，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都至少使用这些辅助因子的一部分。虽然它们在维持基本生化反应中的重要性已被广泛认识，但硫活化、运输和插入辅助因子的机制仍未完全了解。然而，人们普遍认为，在细菌、真核生物和某些古细菌中，游离氨基酸半胱氨酸是大多数含硫辅助因子生物合成的硫的来源。半胱氨酸脱硫酶家族催化硫活化的第一步。该项目将确定生理还原剂——特别是硫氧还毒素和含有硫的小分子（谷胱甘肽、杆菌硫醇和真菌硫醇）——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反应活性的特定蛋白质相互作用。该项目将扩大代表性不足群体的参与，包括来自塞勒姆学院和吉尔福德学院的本科生研究人员，这两所规模较小的本地本科院校。作为共同导师的研究生将获得更好的沟通技巧，为将来成为独立的教师学者做准备。半胱氨酸脱硫酶催化的反应包括形成过硫中间体并将其转移到参与Fe-S簇、tRNA、rRNA和DNA中的硫核苷、生物素、硫辛酸、钼辅因子和硫胺素的生物合成的受体分子。研究硫辅因子生物合成中的硫转移反应具有挑战性。其中一个主要的挑战是硫受体蛋白通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，确定生理还原剂在促进细菌硫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硫转移的生化途径中的作用的基础知识，并将建立控制生物合成酶反应性的进化决定因素。该项目由生物科学理事会分子和细胞生物科学部分子生物物理学组和数学和物理科学理事会化学部生命过程化学组共同支持。

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.