Fueling CO2-fixation by detoxifying CO, what are the secrets behind the electron-bifurcating hydrogenase/formate dehydrogenase from homoacetogens?

通过解毒 CO 来促进 CO2 固定，同型乙酸菌的电子分叉氢化酶/甲酸脱氢酶背后的秘密是什么？

• 批准号: 428142598
• 负责人: Dr. Tristan Wagner
• 金额: --
• 依托单位: Forschungsgruppe Mikrobielle Metabolismen
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/428142598?language=en
• 关键词: Fueling; CO2; fixation; detoxifying; CO

The chemical reduction of CO2 into formate answers to two challenges faced by our modern society: (1) the capture of the atmospheric greenhouse gas CO2; (2) safe long-term storage of the energy generated through renewable sources (e.g. wind, solar…) by using formate as an energy-carrier. Such difficult reaction for chemists is constantly running in microorganisms under standard temperature and pressure. Our proposal aims to decipher the tricks behind this biological CO2-reduction catalyzed by formate dehydrogenase (Fdh), addressing the key question: how enzymes fix CO2 by using low-potential electrons? For this purpose, we will use a model organism that uses CO2-fixation for both, carbon assimilation and energy acquisition: the homoacetogenic bacteria. In natural environments, they play a critical role in organic matter recycling and primary production; in biotechnology, these "bio-converters" turn waste gases (e.g. syngas from steel mill) into biofuels. As waste gases contain high amounts of carbon monoxide (CO), a known inhibitor of Fdh and hydrogenases, cellular CO2-fixation should collapse. However, Clostridium autoethanogenum evolved a genius strategy by converting the poisonous CO as a fuel for the CO2-reduction through the HytA-E/Fdh complex. Electrons from NADPH and reduced ferredoxin, generated during CO­detoxification, are merged in HytA-E through electron bifurcation/confurcation, a biochemical concept recently described in anaerobes. The molecular basis of such trick in HytA-E is unknown, but a new type of tungstopterin-containing Fdh should use the merged electrons to reduce CO2. Since CO-detoxification could saturate Fdh turnover capacities, the system must use an exhauster: an [FeFe]-hydrogenase (HytA), able to evacuate extra electrons by the reduction of protons to H2. Under H2/CO2 condition (without CO), HytA feeds Fdh with electrons from H2. The project aims to elucidate the different key points of the complex: which cofactor operates the electron confurcation/bifurcation event? If a new cofactor is involved, how its biosynthesis and incorporation is performed? How hydrogenase and Fdh cross-talk to synchronize electron repartition? And how does Fdh reduce CO2? Our workflow starts by the cultivation of different homoacetogens under CO, followed by native anaerobic purification and crystallization of HytA-E/Fdh. Structural investigations will provide insights about the global architecture of the machinery, its cofactors composition, electron pathways and the key catalytic residues involved in the CO2-hydrogenation reaction. However, in order to obtain the full image of the mechanistic properties of HytA-E/Fdh, integration and interaction with the other groups among the SPP is indispensable. Complementary analyses through physiology, biophysics, spectroscopy, electro-chemistry and structure-based calculation will confirm our structural hypotheses and expand our views on this revolutionary energy converter.

将二氧化碳化学成分减少为对我们现代社会面临的两个挑战的形式答案：（1）捕获大气温室气体二氧化碳； （2）通过使用形式作为能量载体，可以安全地存储通过可再生能源（例如风，太阳能…）产生的能量。化学家的这种困难反应在了解标准温度和压力的微生物中不断运行。我们的建议旨在破译这种生物二氧化碳还原以形式脱氢酶（FDH）催化的技巧，解决了一个关键问题：酶如何通过使用低电位电子学来修复CO2？为此，我们将使用一个模型组织，该组织使用CO2固定来进行碳同化和能量采集：同源性细菌。在自然环境中，它们在有机物回收和初级生产中起着至关重要的作用。在生物技术中，这些“生物转化器”将废气（例如钢厂的合成气）变成生物燃料。由于废气含有大量的一氧化碳（CO），即已知的FDH和氢化酶抑制剂，因此细胞CO2固定应崩溃。然而，梭状芽胞杆菌自身乙乳杆菌通过将有毒CO转换为通过Hyta-E/FDH复合物减少CO2的燃料来发展一种天才策略。来自NADPH的电子和减少在CodeToxification期间产生的铁氧还蛋白通过电子分叉/碰撞合并在Hyta-E中，这是一种在厌氧菌中最近描述的生化概念。这种技巧在Hyta-E中的分子基础尚不清楚，但是一种新型的含钨的FDH应该使用合并的电子来减少CO2。由于共氧化能力可以使FDH失误容量饱和，因此系统必须使用排气：[FEFE] - 氢化酶（HYTA），能够通过将质子还原为H2来撤离额外的电子。在H2/CO2条件下（无CO），Hyta用来自H2的电子馈送FDH。该项目旨在阐明复合体的不同关键点：哪个辅助因子运行电子结构/分叉事件？如果涉及新的辅助因子，则如何进行其生物合成和合并？氢化酶和FDH串扰如何同步电子重新分配？ FDH如何减少二氧化碳？我们的工作流程始于在CO下培养不同的同型聚物，然后是天然厌氧纯化和Hyta-E/FDH的结晶。结构研究将提供有关机械，其辅助因子组成，电子途径以及涉及二氧化碳 - 氢化反应的关键催化残差的见解。但是，为了获得Hyta-E/FDH的机械性能的完整图像，与SPP之间的其他组的集成和相互作用是必不可少的。通过生理学，生物物理学，光谱，电化学和基于结构的计算进行互补分析将证实我们的结构假设，并扩展我们对这种革命能量转换器的看法。