Probing the mechanism and diversity of multi-electron redox reactions in sulfite

描述(申请人提供)：多电子氧化还原反应，如那些由亚硫酸盐还原酶(SIRS)催化的反应，人们知之甚少，但在许多生物过程中很重要。此外，结核分枝杆菌利用亚硫酸盐还原酶吸收硫，因此是潜在的治疗靶点。SIRS以电子方式将铁血红素与[4Fe-4S]团簇偶联，形成氧化还原活性催化中心。有人提出，亚硫酸盐的六电子还原为硫化物是通过顺序的两电子步骤进行的，然而，人们对催化过程中电子和质子转移的准确顺序和时间知之甚少，也不知道这个复杂的过程是如何在不产生副产物的情况下进行的。同化型(ASiRs)和异化型(DsiR)SIR在结构和辅因子排列上有很大的差异。来自结核分枝杆菌的单体ASIR(MtSiR)在活性部位附近含有一个不寻常的共价连接的半胱氨酸-酪氨酸。来自黄褐古菌的多聚体DSIR(AfSiR)含有第二对siroheme-[4Fe-4S]辅因子，不能与底物结合。研究mtSiR和afSiR的催化机制，与来自大肠杆菌的原型多聚体ASIR(EcSiR)并行，将有助于我们对多电子催化的理解。此外，更好地了解结核分枝杆菌亚硫酸盐还原酶的催化机制可以导致靶向疗法的发展，因此可能对全球健康产生深远影响。该培训计划将需要使用许多生物化学和生物无机化学的常用技术，如电子顺磁共振、UV-Vis光谱以及蛋白质的表达和纯化。因此，它将为学员成为一名成功的生物化学家做好准备。此外，该培训计划提供高度专业化的蛋白质电化学领域的培训，提供蛋白质膜伏安法和电位法等技术方面的培训。完成这项计划后，学员将做好充分准备，成为一名高技能的科学家。

DESCRIPTION (provided by applicant): Multi-electron redox reactions, such as those catalyzed by sulfite reductases (SiRs), are poorly understood, yet important in many biological processes. In addition, Mycobacterium tuberculosis utilizes sulfite reductase in assimilation of sulfur and is therefore a potential target for therapy. SiRs electronically couple a siroheme with a [4Fe-4S] cluster to form a redox-active catalytic center. It has been proposed that the six- electron reduction of sulfite to sulfide occurs via sequential, two-electron steps, however little is known about the precise order and timing of electron and proton transfers that occur during catalysis, or how this complex process is carried out without the formation of side products. Assimilatory (aSiRs) and dissimilatory (dSiR) type SiRs are quite diverse in their structure and cofactor arrangement. The monomeric aSiR from Mycobacterium tuberculosis (mtSiR) contains an unusual covalently-linked Cys-Tyr adjacent to the active site. The multimeric dSiR from Archaeoglobus fulgidus (afSiR) contains a second pair of siroheme-[4Fe-4S] cofactors, unavailable for substrate binding. Investigating the catalytic mechanism of mtSiR and afSiR, in parallel with the prototypical multimeric aSiR from Escherichia coli (ecSiR), will advance our understanding of multi-electron catalysis. In addition, a better understanding of the catalytic mechanism of M. tuberculosis sulfite reductase could lead to the development of targeted therapeutics, and could therefore have a profound impact on global health. This training program will require the utilization of many techniques common to biochemistry and bioinorganic chemistry such as Electron Paramagnetic Resonance, Uv-vis spectroscopy, and protein expression and purification. Hence, it will prepare the participant for a successful career as a biochemist. In addition, the training program offers training in the highly specialized area of protein electrochemistry, offering training in techniques such as Protein Film Voltammetry and potentiometry. Upon completion of this program, the participant will be well prepared to enter the workforce as a highly skilled scientist.