Electron and Proton Transfer in Reaction Centers

描述（由申请人提供）：拟议的研究是对细菌反应中心（RC）中电子和质子转移过程的研究。这些过程在许多其他蛋白质中很重要，并形成生物膜中能量转换的基础。总的目标是提供一个描述的分子基础，这种蛋白质在细胞机械耦合电子转移质子泵跨膜。这项工作主要集中在两个关键过程：1）质子耦合电子转移反应，导致结合泛醌，QB的还原，和2）细胞色素C2和RC之间的蛋白质间电子转移反应。使用光脉冲启动电子转移反应的能力允许详细了解这些反应中涉及的分子过程。将使用定点诱变来研究这些反应的机制。质子偶联反应的电子转移速率是复杂的，并且被认为涉及蛋白质动力学以及质子和电子转移。将通过定点诱变检查观察到的电子转移速率的分子基础，以阐明控制电子转移速率的因素。据信，进入QB位点的质子转移途径涉及表面His残基以及酸性残基和水分子的链。质子转移的重要因素将通过修改质子转移途径中的残留物的环境和使用我们已经开发的方法测量质子转移速率来研究。将检查细胞色素和RC之间的蛋白质间电子转移反应，以测试有关动态对接机制的想法，其中包括在RC表面的细胞色素的结合和电子转移，以及通过溶剂水的电子转移。将通过X射线晶体学和光谱技术（包括电子顺磁共振、电子核双共振和红外光谱）检查具有修改的质子和电子转移速率的突变体的结构。这项研究将有助于阐明在许多生物系统中发现的电子和质子转移机制的分子基础。功能测定、遗传信息和结构生物学的结合提供了对这些重要生物过程的分子基础的理解，并应有助于为分子医学的未来发展奠定基础。

DESCRIPTION (provided by applicant): The proposed research is a study of electron and proton transfer processes in bacterial reaction centers (RC). These processes are important in many other proteins and form the basis for energy conversion in biological membranes. The overall goal is to provide a description of the molecular basis for this protein in cellular machinery that couples electron transfer to proton pumping across the membrane. The work focuses on two key processes; 1) Proton-coupled electron transfer reactions that result in the reduction of a bound ubiquinone, QB, and 2) Inter-protein electron transfer reaction between cytochrome C2 and RC. The ability to initiate the electron transfer reactions using light pulses allows a detailed understanding of the molecular process involved in these reactions. Site directed mutagenesis will be used to investigate the mechanism of these reactions. The electron transfer rates for the proton-coupled reactions are complex and are believed to involve protein dynamics as well as proton and electron transfer. The molecular basis for the observed electron transfer rate will be examined by site directed mutagenesis to elucidate the factors that control the electron transfer rate. The proton transfer pathway into the QB site is believed to involve surface His residues and a chain of acidic residues and water molecules. The factors important for proton transfer will be investigated by modification of the environment of the residues in the proton transfer pathway and measurement of proton transfer rates using methods that we have developed. The inter-protein electron transfer reaction between cytochrome and RC will be examined to test ideas concerning dynamic docking mechanisms, which involves binding and electron transfer of cytochrome at the RC surface, and electron transfer through solvent water. The structures of the mutants with modified proton and electron transfer rates will be examined by X-ray crystallography, and spectroscopic techniques including electron paramagnetic resonance, electron nuclear double resonance and infrared spectroscopy. The proposed research would help elucidate the molecular basis for electron and proton transfer mechanisms found in many biological systems. The combination of functional assays, genetic information and structural biology provide an understanding of the molecular basis these important biological processes and should help lay the foundations for future advances in molecular medicine.