Complementary Studies of Native Sulfite Reductase and Biosynthetic Model to Understand Structural Features Responsible for Selective Multi-Electron Reduction of Sulfite

项目概要/摘要 这个项目的目标是获得详细的了解结构特点目前 在一类多核金属酶，使其能够促进选择性6 e- 减少亚硫酸盐（SiRs），并解决复杂领域的重要科学问题 多核过渡金属活性中心和全球硫循环。具体而言，该项目旨在 为了理解耦合辅助[4Fe-4S]团簇还原势在促进 亚硫酸盐的有效和选择性的S-O键断裂，沿着 在SiRs的催化循环中已经提出的中间体。为了实现这一目标， 该项目提出了对天然SiR蛋白和生物合成模型的补充研究 能够催化亚硫酸盐还原-SiRs目前唯一的结构和功能模型。 使用一种新的生物合成方法，其目的是克服研究固有的局限性， 单独的天然酶，一个强大的支架将用于了解SiR的哪些特征是至关重要的 通过旨在显示功能增益的实验，而不是推断 结构-功能关系通过天然酶活性的丧失。拟议 这两个系统的互补研究将使我们能够确定独特的结构特征， 到SiR，其导致对复杂的多电子、多质子的高催化效率， 转型我们将能够理解：（1）氧化还原活性[4Fe-4S]的重要性 簇偶联到siroheme底物结合位点对SiR活性的影响，（2）假设的性质 Fe-SOx中间体及其与SiR催化循环的关系;（3）SiR催化循环的特征 SiR中的siroheme配体使其适合于亚硫酸盐还原活性，相对于血红素c 生物合成支架。 实现上述目标将导致对结构和功能的更深入理解 这可能难以通过单独研究天然酶来实现。通过模拟 通过用不同的蛋白质支架进行合理的修饰来实现天然系统的功能， 可以得出关于本族的重要结构特征的可推广的结论。 活性部位这项研究计划将促进对广泛的多核核 与人类健康相关的金属酶，特别是与其结构、功能和 金属酶设计一般，同时提供了一个极好的培训机会，以实现 候选人的职业目标。

Project Summary/Abstract The goal of this project is to obtain detailed understanding of the structural features present in a class of multinuclear metalloenzymes that make it capable of promoting selective 6 e- reduction of sulfite (SiRs), and address important scientific issues in the fields of complex multinuclear transition metal active sites and the global sulfur cycle. Specifically, this project seeks to understand the role of the coupled auxiliary [4Fe-4S] cluster reduction potential on facilitating efficient—and selective—S-O bond cleavage of sulfite, along with the chemical nature of intermediates that have been proposed in the catalytic cycle of SiRs. To achieve this goal, this project proposes complimentary studies, both of a native SiR protein, and a biosynthetic model capable of catalyzing sulfite reduction—the only current structural and functional model of SiRs. Using a novel biosynthetic approach, which aims to overcome limitations inherent to studies of the native enzyme alone, a robust scaffold will be used to learn which features of SiR are crucial for its activity, through experiments designed to display a gain in function, as opposed to inferring structure-function relationship through loss of activity in the native enzyme. The proposed complimentary studies of these two systems will allow us to identify the structural features unique to SiRs that lead to high catalytic efficiency towards a complex multi-electron, multi-proton transformation. We will be able to understand: (1) the importance of the redox active [4Fe-4S] cluster coupled to the siroheme substrate binding site on SiR activity, (2) the nature of postulated Fe-SOx intermediates, and their relevance to the catalytic cycle of SiR, and (3) the features of the siroheme ligand in SiR which make it suitable for sulfite reduction activity, relative to the heme c of the biosynthetic scaffold. Achieving the above goals will result in a deeper understanding of the structure and function of SiRs that may be difficult to achieve by studying the native enzyme alone. By mimicking the function of a native system through rational modifications with a different protein scaffold, generalizable conclusions can be made concerning important structural features of the native active site. This research plan will advance the knowledge of a broad range of multinuclear metalloenzymes relevant to human health, specifically, related to their structure, function, and metalloenzyme design in general, while providing an excellent training opportunity to achieve the career goal the candidate.