NSF/BIO-DFG: Biological Fe-S intermediates in the synthesis of nitrogenase metalloclusters

氮气（N2）是地球上最丰富的氮源。然而，这种营养来源只有一小部分微生物才能从生物学上获得，这些微生物可以将其还原成NH4+铵。生物固定N2的能力是生物地球化学氮循环的关键步骤，对地球上的生命至关重要。负责该反应的酶是氮酶，其活性依赖于其相关的金属辅助因子。本项目旨在阐明由NifU和NifS蛋白促进的氮酶金属辅助因子合成的初始反应步骤。先前的研究已经确定这些蛋白质参与了支持初始铁硫（Fe-S）构建块的合成，用于氮酶金属辅助因子。该奖项支持的研究将探索NifU和NifS如何在模式细菌Azotobacter vinelandii中组装这些Fe-S单元。这个跨学科的国际合作项目将通过研究经验和专业发展机会吸引本科生和研究生。德国和美国的PI伙伴关系将支持两项协同研究和专业发展努力：(A)为研究生提供国外合作研究经验，(b)为当地本科生提供指导研究奖学金。这些努力与培养下一代STEM领导者以适应多样化和全球化的劳动力相关。该项目旨在研究在自然环境和生理还原剂存在的情况下Fe-S簇合成的机制和化学步骤，通过建立1)与NifU相关的新簇物种的位置和光谱特征，2)参与该过程的其他因素，以及3)新发现的簇物种作为合成氮酶金属簇的基础的反应性。揭示固氮的分子和机制细节对于理解它们在整个进化过程中持续和保守的需求具有内在的智力价值。这些原则也可以指导在更复杂的系统中利用金属辅助因子参与其他细胞过程的Fe-S簇的基础研究。这个美国/德国合作项目由美国国家科学基金会（化学和分子与细胞生物科学部联合）和德国研究基金会（DFG）支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nitrogen gas (N2) is the most abundant source of nitrogen on Earth. However, this nutrient source is only biologically accessible to a subset of microbes that can reduce it into ammonium NH4+. The biological capacity to fix N2 is a critical step in the biogeochemical nitrogen cycle and essential to life on Earth. The enzyme responsible for this reaction is nitrogenase and its activity relies on its associated metallocofactors. This project aims to elucidate initial reaction steps involving the synthesis of nitrogenase metallocofactors that are promoted by proteins NifU and NifS. Previous studies have established the involvement of these proteins in supporting the synthesis of initial iron-sulfur (Fe-S) building blocks for nitrogenase metallocofactors. The research supported by this award will explore how NifU and NifS assemble these Fe-S units in the model bacterium Azotobacter vinelandii. The interdisciplinary, collaborative international project will engage undergraduate and graduate students through research experiences and professional development opportunities. A German and an American PI partnership will support two synergistic research and professional development efforts: (a) collaborative research experiences abroad for graduate students and (b) mentored research fellowships for local undergraduate students. These efforts are relevant for preparing the next generation of STEM leaders for a diverse and globalized workforce. The project is aimed at investigating the mechanistic and chemical steps of Fe-S cluster synthesis in the context of a native environment and the presence of physiological reductants by establishing 1) the location and spectroscopic features of novel cluster species associated with NifU, 2) the involvement additional factors in this process, and 3) the reactivity of newly identified cluster species as building blocks for the synthesis of nitrogenase metalloclusters. Uncovering molecular and mechanistic details that enable nitrogen fixation has intrinsic intellectual merit in understanding their sustained and conserved requirement throughout evolution. These principles can also guide foundational studies on Fe-S clusters on more complex systems that utilize metallocofactors participating in other cellular processes. This collaborative US/Germany project is supported by the US National Science Foundation (Chemistry and Molecular and Cellular Biosciences Divisions jointly) and the German Research Foundation (DFG).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.