Structural Basis for Electron Transfer between the Bacterial Reaction Center and Cytochrome C2 in Rhodobacter Sphaeroides

球形红杆菌细菌反应中心和细胞色素 C2 之间电子转移的结构基础

• 批准号: 9974568
• 负责人: Melvin Okamura
• 金额: $ 37.5万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2002-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9974568&HistoricalAwards=false
• 关键词: Structural; Basis; Electron; Transfer; between

OkamuraMCB 9974568The aim of this research is to determine the molecular basis for the electron transfer reaction between cytochrome c2 and the bacterial reaction center (RC). These studies will build upon recent advances in the x-ray co-crystal structure of the cytochrome c2/RC complex that show the cytochrome to be docked on the RC through a hydrophobic contact region forming a direct electron transfer pathway between heme and bacteriochlorophyll cofactors. The questions to be addressed concern the structure of the complex between the RC and cytochrome c2 and the mechanism of interprotein electron transfer. Site directed mutations on both RC and cytochrome will be constructed and the effects of these mutations on binding and rates of electron transfer will be determined. The effects of the mutations on the binding of the cytochrome will be used to give information about the relative importance of electrostatic and hydrophobic contributions. The effects of mutations on the collision rate of electron transfer will give information about the conformational dynamics involved in the protein association and electron transfer. These studies will also be extended to the effects on the electron transfer process in chromatophore membranes in order to explore the relative effects of the cytochrome RC interaction in modulating the overall efficiency of photosynthetic electron transfer. The membranes of photosynthetic bacteria contain the molecular machinery that permits the efficient conversion of light energy into chemical energy. The energy conversion requires a light induced charge separation in a protein called the reaction center, followed by rapid electron transfer through a chain of electron carriers that are arranged to do chemical work by pumping protons across the membrane. This research is aimed at investigating the structural basis for electron transfer to the light activated reaction center mediated by cytochrome c2. The reaction between cytochrome c2 and the RC in photosynthetic bacteria displays both a specificity in binding and high rate of interprotein electron transfer that are necessary to maintain a fast electron transfer through the electron transfer chain. These studies of the binding and electron transfer reactions between cytochrome c2 and the bacterial RC should provide the basis for understanding the energy conversion process in photosynthesis.

本研究的目的是确定细胞色素c2与细菌反应中心（RC）之间电子转移反应的分子基础。这些研究将建立在细胞色素c2/RC复合物的x射线共晶结构的最新进展的基础上，该结构表明细胞色素通过疏水接触区停靠在RC上，形成血红素和细菌叶绿素辅助因子之间的直接电子转移途径。要解决的问题是RC和细胞色素c2之间复合物的结构和蛋白质间电子转移的机制。将构建RC和细胞色素的位点定向突变，并确定这些突变对结合和电子转移速率的影响。突变对细胞色素结合的影响将用于提供有关静电和疏水贡献的相对重要性的信息。突变对电子转移碰撞率的影响将提供有关蛋白质结合和电子转移的构象动力学的信息。这些研究还将扩展到对染色质膜中电子转移过程的影响，以探索细胞色素RC相互作用在调节光合电子转移总体效率方面的相对作用。光合细菌的膜包含分子机制，使光能有效地转化为化学能。能量转换需要在一种叫做反应中心的蛋白质中进行光诱导电荷分离，然后通过一系列电子载体进行快速的电子转移，这些电子载体通过泵送质子穿过膜来完成化学功。本研究旨在探讨细胞色素c2介导的电子向光活化反应中心转移的结构基础。在光合细菌中，细胞色素c2与RC的结合具有特异性和高的蛋白质间电子转移率，这是维持快速电子转移链所必需的。这些细胞色素c2与细菌RC之间的结合和电子转移反应的研究为理解光合作用中的能量转换过程提供了基础。