Structure and Function of Photosystem I

Biggins 9404744该研究是对光合反应中心，光系统1的结构和功能的两个相关目标的研究。 1)第一个目标是继续研究的核心heterodimer，它承担的辅助因子的电荷分离和早期电子转移受体，与一个小的亚基PsaC进行终端铁硫中心的相互作用的机制。这将通过在核心异二聚体中的PsaC亚基的推定结合结构域中和PsaC亚基本身上产生定点突变来实现。 将遵循电子转移反应，以确定在体外使用PsaC、PsaD和簇插入方案重建异二聚体的成功。 2)第二个目标是继续调查叶绿醌作为一个短暂的受体的核心异二聚体的功能。次级醌在光系统1中的作用仍然难以捉摸，我们提出实验来确定其在反应中心的初级光化学中的可能功能。我们已经表明，参与正向电子转移的伯醌的结合位点可以被抑制。我们将更详细地研究抑制作用，以研究醌结合位点的性质并选择新的抑制剂。在这一领域的基础研究是重要的，因为潜在的开发除草剂选择性的光系统1。 原申请中提出的关于蛋白质设计的第三个目标将不会实现，因为该奖项缺乏足够的资金。 这项在国家科学基金会赞助下继续进行的研究涉及光合作用的机理。 光合作用是植物生物学中的一个基本过程，太阳能被用来提供从大气中吸收二氧化碳的驱动力，并将其转化为植物所需的所有不同产品。这是生物太阳能转换的唯一形式，动物的生命依赖于这个过程来生产所有的食物。我们还依靠这一过程生产用于建筑、纸张、包装和无数其他材料的林产品。目前正在消耗的所有化石燃料，如石油、天然气和煤炭，都是通过史前植物对太阳能的光合作用转化而产生的。 植物的光合作用过程发生在叶组织的生物膜中，并且可以在实验室中分离称为反应中心的太阳能转换酶系统。目前正在对这些反应中心的原子结构及其化学功能的细节进行研究。 该项目的具体工作集中在结构-功能方面，使用生物化学技术将反应中心解离成积极参与太阳能转换过程的单个蛋白质和分子，以便对其进行识别和表征。分子遗传学方法用于改变这些蛋白质，以提供有关其功能的信息。 光合作用研究的理由是，当反应中心功能的机制得到阐明时，它将导致： 增加粮食产量和用于纤维、建筑材料和液体燃料的生物量，如乙醇，乙醇目前与汽油混合使用，用于更清洁的汽车。 在将太阳光直接转化为电能方面，与光伏电池竞争的设备工程。光生氢作为燃料。 设计选择性除草剂以控制农作物和森林生产力。

Biggins 9404744 The research is an investigation with two related objectives on the structure and function of the photosynthetic reaction center, Photosystem 1. 1) The first objective is a continuation of studies on the mechanism ofinteraction of the core heterodimer, which bears the cofactors for charge separation and early electron transfer acceptors, with a small subunit PsaC which carries the terminal iron sulfur centers. This will be accomplished by creating site directed mutations in the putative binding domain of the PsaC subunit in the core heterodimer and on the PsaC subunit itself. Electron transfer reactions will be followed to determine the success of the reconstitutions of the heterodimer using PsaC, PsaD and cluster insertion protocols in vitro. 2) The second objective is a continuation of investigations concerning the function of phylloquinone as a transient acceptor on the core heterodimer. The role of the secondary quinone in Photosystem 1 remains elusive, and we propose experiments to determine its possible function in the primary photochemistry of the reaction center. We have shown that the binding site of the primary quinone involved in forward electron transfer can be inhibited. We will investigate the inhibition in more detail to study properties of the quinone binding site and select new inhibitors. Basic research in this area is important because of the potential for developing herbicides selective for Photosystem 1. The third objective on protein design proposed in the original request will not be pursued because of a lack of sufficient funds in the award. %%% This research to be continued under the auspices of the National Science Foundation concerns the mechanism of photosynthesis. Photosynthesis is a fundamental process in plant biology whereby solar energy is used to provide the driving force for the uptake of carbon dioxide from the atmosphere and its conversion into all the different products needed for the plant. This is the only form of biosolar conversion and animal life depends upon this process for the production of all food. We also rely on this process for the generation of forest products for construction, paper, packaging and countless other materials. The origin of all fossil fuels such as oil, gas and coal now presently being expended was via a photosynthetic conversion of solar energy by prehistoric plants. The process of photosynthesis in plants occurs in biological membranes in the leaf tissue and it is possible to isolate the solar conversion enzyme systems called reaction centers in the laboratory. Progress is now being made on details of the atomic structure of these reaction centers and their chemical function. The specific work in this project focuses on structure-function aspects using biochemical techniques to dissociate the reaction centers into the individual proteins and molecules actively involved in the solar conversion process so they can be identified and characterized. Molecular genetic methods are used to make alterations in these proteins to provide information on their function. The justification of research in photosynthesis is that when a complete understanding of the mechanism of reaction center function has been elucidated it will lead to: increased yields of food and biomass for fiber, construction materials andliquid fuels such as ethyl alcohol which is presently being used in mixtures with gasoline for cleaner automobile use. the engineering of devices that would be competitive with photovoltaic cell for the direct conversion of sunlight into electricity. the photo-production of hydrogen as a fuel. the design of selective herbicides for the control of crops and fores productivity.