Design Principals of Photobiological Metabolism

描述（由申请人提供）：细胞代谢包括生物体获取、储存和释放响应不断变化的需求和环境条件所需因子的基本过程。在进行光合作用的生物体中，细胞代谢的基础来自对太阳能的有控制的捕获和利用，这一过程对几乎所有陆地生命都是必不可少的。在化学上，光合作用的早期反应涉及吸收入射太阳光并将其转化为低电位电子，这些电子可用于驱动各种代谢过程，包括碳固定。电子通量朝向不同代谢过程的方向的调节主要通过电子载体铁氧还蛋白的作用来控制。然而，铁氧还蛋白优先将低电位电子提供给一种代谢途径而不是另一种代谢途径的机制却知之甚少。为此，我建议研究铁氧还蛋白内的蓝藻细长聚球藻PCC 7942的电子通量的可塑性。具体来说，我提出了一系列的实验，旨在重新定向低电位电子对细胞氢化酶，催化氢气的生产作为一个读出接受的电子。建议的实验涉及蓝细菌菌株的建设与诱导下调的代谢途径竞争低电位电子，以及菌株与铁氧还蛋白和氢化酶空间上限制在一起的嵌合蛋白或合成蛋白支架的表达。这些实验将导致能够直接从阳光中产生氢气的蓝细菌菌株的构建。这些实验的结果将对理解光合作用代谢具有相关性。此外，这些实验将对光合作用驱动的生物医学化合物和可持续清洁生物燃料生产途径的工程设计产生广泛影响。 公共卫生相关性：拟议的研究需要研究早期的蓝藻光合作用反应，这些反应涉及将捕获的太阳能转化为不同的生物代谢产物。对这些过程的深入了解可以用于光合生物的再工程，以产生替代的、经济上相关的代谢物。光驱动的生物途径可以为生产化学化合物（如药物和/或生物燃料）的新颖且廉价的方法提供基础。

DESCRIPTION (provided by applicant): Cellular metabolism encompasses the fundamental processes by which organisms acquire, store, and release factors required to respond to changing needs and environmental conditions. In photosynthesizing organisms, the basis for cellular metabolism is drawn from the controlled capture and utilization of solar energy, a process which is essential for virtually all terrestrial life. Chemically, the early reactions of photosynthesis involve the absorption of incident solar light and its conversion into low potential electrons that can be used to drive a variety of metabolic processes, including carbon fixation. Regulation of the direction of electron flux towards different metabolic processes is largely controlled through the actions of the electron carrier, ferredoxin. However, the mechanism by which ferredoxin preferentially donates low potential electrons to one metabolic pathway over another is poorly understood. To this end, I propose to examine the plasticity of electron flux from ferredoxin within the cyanobacterium Synechococcus elongatus PCC7942. Specifically, I propose a series of experiments designed to redirect low potential electrons towards cellular hydrogenases, which catalyze the production of hydrogen gas as a readout of accepted electrons. Proposed experiments involve the construction of cyanobacterial strains with inducible downregulation of metabolic pathways competing for low potential electrons as well as strains with ferredoxin and hydrogenases spatially constrained together by expression of chimeric proteins or synthetic protein scaffolds. These experiments will result in the construction of strains of cyanobacteria capable of producing hydrogen gas directly from sunlight. The results of these experiments will have relevance for the understanding of photosynthetic metabolism. Furthermore, these experiments will have broad implications for the engineering of photosynthesis-driven pathways for the production of biomedical compounds and sustainable, clean biofuels. PUBLIC HEALTH RELEVANCE: Proposed research entails the study of early cyanobacterial photosynthesis reactions which are involved with the conversion of captured solar energy into distinct biological metabolites. A deeper knowledge of these processes can be leveraged for the re-engineering of photosynthetic organisms to produce alternate, economically-relevant metabolites. Light-driven biological pathways can provide the basis for novel and inexpensive approaches for the production of chemical compounds, such as pharmaceuticals and/or biofuels.