CAREER: CO2 activation by nitrogenase Fe proteins

化学系的生命过程化学项目将资助加州大学欧文分校的胡伊琳博士研究固氮酶的铁蛋白对二氧化碳的激活作用，固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品是同时应对二氧化碳排放增加和化石燃料供应减少问题的有效战略。然而，二氧化碳的活化或分解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。这项研究的重点是简单的铁硫酶是如何发生反应的，这将为未来适应这种新型反应提供一个关键框架，将温室气体二氧化碳循环利用成有用的产品。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，将这项研究纳入到对现有学生的培训和对未来学生的推广中，提高了公众对这一研究路线的重要性的兴趣和认识，因此对后代的教育具有更广泛的影响。本项目研究了固氮酶铁蛋白在体外激活二氧化碳的机制，并利用铁蛋白的表达构建了一株能够提高体内二氧化碳还原效率的棕色固氮菌菌株。在理论计算的指导下，这项拟议的研究结合了遗传、生化、光谱和结构方法来解决全铁蛋白还原二氧化碳的独特反应，并解决了与该反应机制相关的几个基本问题。此外，筛选和表达策略的结合被用来鉴定具有更高二氧化碳还原效率的铁蛋白或同系物，并提高二氧化碳还原过程中铁蛋白的电子转移的特异性。这些研究的结果为以下方面提供了重要的见解：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，以及从对A.vinelandii的研究中可以得出哪些原则，为未来开发具有成本效益的、全细胞的二氧化碳转化策略提供了重要的见解。

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.