CAREER: CO2 activation by nitrogenase Fe proteins

凭借这一奖项，化学学部的生命过程化学项目资助了加州大学欧文分校的Yilin Hu博士，以研究氮酶的铁蛋白对二氧化碳的激活作用，氮酶是微生物中负责固氮的酶。将温室气体二氧化碳转化为有价值的化学物质是一种有效的战略，可以同时解决向大气中排放的二氧化碳增加和化石燃料供应减少的问题。然而，二氧化碳的活化或分裂通常需要高温高压条件，这给我们的能源供应和环境健康带来了巨大的负担。这项研究的重点是研究一种简单的铁硫酶是如何发生这种反应的，这将为未来适应这种新型反应，将温室气体二氧化碳回收为有用的产品提供一个关键的框架。因此，它通过解决我们当今面临的两个最重要的挑战：化石燃料枯竭和气候变化，对我们的社会产生了广泛的科学影响。此外，将这项研究纳入现有学生的培训和对未来学生的推广，提高了公众对这一研究领域重要性的兴趣和认识，因此，对后代的教育产生了更广泛的影响。本项目研究了氮氧化酶铁蛋白在体外激活二氧化碳的机制，并对一株通过表达铁蛋白而提高体内二氧化碳还原效率的固氮菌进行了工程改造。在理论计算的指导下，本研究采用遗传学、生物化学、光谱学和结构学等多种方法来解决全亚铁蛋白还原二氧化碳的独特反应，并解决与该反应机制相关的几个基本问题。进一步，采用筛选和表达相结合的策略，鉴定出具有更高二氧化碳还原效率的铁蛋白或同源物，并提高二氧化碳还原过程中电子向铁蛋白转移的特异性。这些研究的结果提供了重要的见解，了解铁硫基催化剂如何在环境条件下影响二氧化碳的活化和还原，以及从葡萄球菌的研究中可以得出哪些原则，以促进未来开发成本效益高的、基于全细胞的二氧化碳转化策略。

With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Yilin Hu from the University of California, Irvine, to investigate carbon dioxide activation by the iron protein of nitrogenase, the enzyme responsible for nitrogen fixation in microorganisms. Conversion of the greenhouse gas carbon dioxide into valuable chemicals represents an effective strategy to simultaneously combat the problems of increased carbon dioxide emission into the atmosphere and the decreased supply of fossil fuels. However, activation or splitting of carbon dioxide normally requires high temperature and pressure conditions, which puts a tremendous burden on our energy supply and environmental wellness. This pursuit focuses on just how the reaction takes place by a simple iron-sulfur enzyme, which will provide a crucial framework for future adaptations of this novel type of reaction for recycling the greenhouse gas carbon dioxide into useful products. As such, it has broad scientific impacts on our society by addressing two of the most important challenges we face nowadays: fossil fuel depletion and climate change. In addition, incorporation of this research into training of current students and outreach to prospective students raises public interest and awareness of the importance of this line of research and, therefore, has broader impacts on the education of future generations.This project investigates the mechanism of in vitro carbon dioxide activation by the iron protein of nitrogenase and the engineering of an Azotobacter vinelandii strain with improved efficiency of in vivo carbon dioxide reduction upon expression of the iron protein. Guided by theoretical calculations, the proposed research employs a combination of genetic, biochemical, spectroscopic and structural approaches to tackle the unique reaction of carbon dioxide reduction by the all-ferrous iron protein and address several fundamental questions related to the mechanism of this reaction. Further, a combination of screening and expression strategies are used to identify iron proteins or homologs with higher efficiencies of carbon dioxide reduction and improve the specificity of electron transfer to the iron protein during the process of carbon dioxide reduction. The outcome of these studies provides important insights into how iron-sulfur based catalysts work to effect carbon dioxide activation and reduction under ambient conditions and what principles can be derived from studies of A. vinelandii for future development of cost-efficient, whole-cell-based strategies for carbon dioxide conversion.