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

描述（由申请人提供）：多电子氧化还原反应，如由亚硫酸盐还原酶（SiRs）催化的反应，目前了解甚少，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同化硫，因此是一个潜在的治疗目标。SiRs将siroheme与[4Fe-4S]簇电子偶联以形成氧化还原活性催化中心。已经提出亚硫酸盐到硫化物的六电子还原经由连续的两电子步骤发生，然而关于在催化过程中发生的电子和质子转移的精确顺序和时间，或者如何在不形成副产物的情况下进行该复杂过程知之甚少。同化型（aSiR）和异化型（dSiR）SiR在结构和辅因子排列上有很大差异。来自结核分枝杆菌的单体aSiR（mtSiR）含有与活性位点相邻的不寻常的共价连接的Cys-Tyr。来自闪烁古生球菌的多聚体dSiR（afSiR）含有第二对siroheme-[4Fe-4S]辅因子，其不可用于底物结合。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）平行，将推进我们对多电子催化的理解。此外，对M.结核病亚硫酸盐还原酶可能导致靶向疗法的发展，因此可能对全球健康产生深远影响。该培训计划将需要利用生物化学和生物无机化学的许多常见技术，如电子顺磁共振，紫外可见光谱，蛋白质表达和纯化。因此，它将为参与者作为生物化学家的成功职业生涯做好准备。此外，该培训计划还提供蛋白质电化学高度专业化领域的培训，提供蛋白质薄膜伏安法和电位法等技术培训。完成该计划后，参与者将为成为一名高技能科学家做好充分准备。

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.