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

项目摘要/摘要 本项目的目标是详细了解现有的结构特征。 在一类多核金属酶中，使其能够促进选择性6e- 减少亚硫酸盐(SIRS)，并解决复杂环境领域的重要科学问题 多核过渡金属活性中心与全球硫循环。具体地说，这个项目寻求 了解偶联辅助[4Fe-4S]团簇还原电势在促进 亚硫酸盐的高效和选择性的S-O键断裂以及 在SIRS的催化循环中提出的中间体。为了实现这一目标，这 该项目提出了免费研究，包括对天然SIR蛋白和生物合成模型的研究 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，旨在克服研究的固有限制 仅仅是天然的酶，一个强大的支架将被用来了解SIR的哪些特征是至关重要的 对于它的活动，通过设计的实验来显示功能上的收益，而不是推断 通过失去天然酶的活性而产生的结构-功能关系。建议数 对这两个系统的免费研究将使我们能够识别独特的结构特征 导致对复杂的多电子、多质子的高催化效率的SIRS 转型。我们将能够理解：(1)氧化还原活性的重要性[4Fe-4S] 偶联到Siroheme底物结合部位的簇对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，以及(3) SIR中的Siroheme配体，相对于血红素c，使其适合于亚硫酸盐还原活性 生物合成的支架。 实现上述目标将导致对结构和功能的更深入理解 仅通过研究天然酶可能很难实现这一点。通过模仿 通过用不同的蛋白质支架进行合理的修饰来发挥天然系统的功能， 关于本地人的重要结构特征，可以得出一般性的结论 活动站点。这项研究计划将推进对广泛的多核分子的认识 与人类健康有关的金属酶，特别是与它们的结构、功能和 一般的金属酶设计，同时提供了一个很好的培训机会来实现 求职者的职业目标。

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.