Design Principals of Photobiological Metabolism

描述（由申请人提供）：细胞代谢包括生物体获取、储存和释放对不断变化的需求和环境条件作出反应所需因子的基本过程。在光合作用生物中，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。从化学上讲，光合作用的早期反应包括吸收入射的太阳光线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。电子通量向不同代谢过程方向的调节主要是通过电子载体铁氧还蛋白的作用来控制的。然而，铁氧还蛋白优先向一种代谢途径提供低电位电子而不是另一种代谢途径的机制尚不清楚。为此，我建议研究铁氧还蛋白在蓝藻长聚球菌PCC7942内的电子通量的可塑性。具体来说，我提出了一系列旨在将低电位电子定向到细胞氢化酶的实验，这种酶作为接受电子的读数催化氢气的产生。拟议的实验包括构建可诱导下调代谢途径竞争低电位电子的蓝藻菌株，以及通过表达嵌合蛋白或合成蛋白支架将铁氧还蛋白和氢化酶空间限制在一起的菌株。这些实验将导致能够直接从阳光中产生氢气的蓝藻菌株的构建。这些实验的结果将对理解光合代谢具有重要意义。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的影响。

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.