CAREER: Manipulating Directionality of Electron Transfer Within Type 1 Photosynthetic Reaction Centers

职业：操纵 1 型光合反应中心内电子转移的方向性

• 批准号: 0347935
• 负责人: Kevin Redding
• 金额: $ 67.15万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0347935&HistoricalAwards=false
• 关键词: CAREER; Manipulating; Directionality; Electron; Transfer

Photosynthetic reaction centers (RCs) are one of life's most ancient and useful devices, allowing the biosphere to exploit the abundant solar energy continuously striking our planet and to diversify into a huge number of species with distinct bioenergetic strategies. All known RCs have symmetric structures, using two similar or identical integral membrane subunits to form a dimeric core, which binds the cofactors through which electrons are transferred across the membrane. This symmetric arrangement gives rise to two similar branches of cofactors down which light-driven electron transfer could proceed. The first two members of each branch are chlorins, while the third is a quinone. It is known that the initial electron transfer occurs almost exclusively along one of the two branches in the well-characterized type 2 RCs, although the origins of this strong asymmetry are still debated. Photosystem I (PS1) is still the best-characterized representative of the type 1 RCs, but many aspects of the direction of electron transfer in PS1 remain unknown. Recent optical work clearly suggests that electron transfer can make use of both cofactor branches of PS1 at ambient temperature, while electron paramagnetic resonance (EPR) data indicate that only one branch is active at low temperature. The purpose of this project is to explore the nature, origins, and degree of bi-directionality of electron transfer in PS1. This will be accomplished mainly by genetic manipulation of the PS1 core polypeptides to bias the partitioning of electrons between the two pathways. The effect of the manipulations will be assessed by time-resolved optical and EPR spectroscopy, which should be capable of distinguishing between the phylloquinone molecules in each branch of PS1, thus providing an assessment of the relative use of each pathway. Mutations near the primary electron donor and acceptors may influence the degree to which ET occurs down the two pathways in predictable ways. The role of external conditions and temperature in determining the utilization of the two branches will also be explored. Ultimately, the long-term goal is to deduce the general rules used by nature to direct light-driven electron transfer.Broader impacts of this work include the training of graduate students and undergraduate students in interdisciplinary science at the interface of chemistry, biology, and physics. It will strengthen ties between several research groups, especially the Redding group and that of Fabrice Rappaport and Pierre Joliot at the Institut de Biologie Physico-Chimique (IBPC, Paris). Moreover, this particular international collaboration will be enlarged by the engagement of a postdoctoral fellow who will spend a considerable amount of time at the IBPC, using their instruments. This project will help to build up the EPR facilities at the University of Alabama, which has already attracted collaborative efforts from several nearby institutes. Finally, the knowledge and expertise gained may have practical aspects, such as the ability to re-engineer RCs, so that partitioning between the two branches becomes responsive to external stimuli (e.g. small ions, binding of hydrophobic ligands, electric field, etc.) and may be directed in a controlled way.

光合反应中心（RC）是生命中最古老和最有用的设备之一，使生物圈能够利用不断撞击我们星球的丰富太阳能，并以独特的生物能源策略多样化为大量物种。所有已知的RC都具有对称结构，使用两个相似或相同的整合膜亚基形成二聚体核心，其结合电子穿过膜转移的辅因子。这种对称的排列产生了两个类似的辅因子分支，光驱动的电子转移可以沿着这两个分支进行。每个分支的前两个成员是二氢卟酚，而第三个是醌。它是已知的，最初的电子转移发生几乎完全沿着的两个分支之一，在良好的特点2型RC，虽然这种强烈的不对称性的起源仍然有争议。光系统I（PS1）仍然是1型RC的最佳表征代表，但PS1中电子转移方向的许多方面仍然未知。最近的光学工作清楚地表明，电子转移可以利用两个辅因子分支的PS1在环境温度下，而电子顺磁共振（EPR）的数据表明，只有一个分支是活跃的在低温下。本研究的目的是探索PS1中电子转移的性质、起源和双向性程度。这将主要通过PS1核心多肽的遗传操作来实现，以偏置两种途径之间的电子分配。操作的效果将通过时间分辨光学和EPR光谱进行评估，其应该能够区分PS 1的每个分支中的叶绿醌分子，从而提供每个途径的相对使用的评估。主要电子供体和受体附近的突变可能以可预测的方式影响ET在两条途径中发生的程度。还将探讨外部条件和温度在确定这两个分支的利用率方面的作用。最终，长期目标是推导出自然界用于指导光驱动电子转移的一般规则。这项工作的更广泛影响包括培养研究生和本科生在化学，生物学和物理学的交叉科学方面的能力。它将加强几个研究小组之间的联系，特别是雷丁小组和生物物理化学研究所（IBPC，巴黎）的Fabrice Rappaport和Pierre Joliot的小组。此外，这一特殊的国际合作将通过一名博士后研究员的参与而扩大，该博士后研究员将在IBPC花费相当长的时间，使用他们的仪器。该项目将有助于在亚拉巴马大学建立EPR设施，该设施已经吸引了附近几个研究所的合作努力。最后，所获得的知识和专业知识可能具有实际方面，例如重新设计RC的能力，使得两个分支之间的划分变得对外部刺激（例如，小离子，疏水配体的结合，电场等）有反应。并且可以以受控的方式被引导。