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

OkamuraMCB 9974568本研究旨在确定细胞色素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，该复合物显示细胞色素通过形成血红素和细菌叶绿素辅因子之间的直接电子转移途径的疏水接触区域停靠在RC上。 待解决的问题涉及RC和细胞色素c2之间的复合物的结构和蛋白质间电子转移的机制。将构建RC和细胞色素的定点突变，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速率的影响将提供有关蛋白质缔合和电子转移中构象动力学的信息。 这些研究也将扩展到色素细胞膜上的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的整体效率的相对影响。 光合细菌的细胞膜包含了将光能有效转化为化学能的分子机制。 能量转换需要在蛋白质中光诱导的电荷分离，称为反应中心，然后通过电子载体链进行快速电子转移，这些电子载体被安排通过泵送质子穿过膜来进行化学工作。 本研究旨在探讨细胞色素c2介导的光活化反应中心电子转移的结构基础。光合细菌中细胞色素c2和RC之间的反应显示出结合的特异性和高速率的蛋白质间电子转移，这是通过电子转移链维持快速电子转移所必需的。 细胞色素c2和细菌RC之间的结合和电子转移反应的这些研究应提供理解光合作用中的能量转换过程的基础。

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.