Electron and Proton Transfer in Reaction Centers

描述(申请人提供)：拟议的研究是关于电子和质子转移反应的研究，这些反应对膜蛋白质中的能量转换过程非常重要。研究了球形红细菌在光合作用反应中心(RC)结合的泛醌QB的反应。2E-2H QB--&gt；QBH2。我们将利用定点突变来研究质子耦合电子转移的机制以及质子转移的途径和机制。这些反应的电子转移速率是复杂的，被认为涉及蛋白质动力学和质子转移。观察到的电子转移速率的分子基础将通过定点突变来研究，以阐明控制电子转移速率的因素。进入QB位点的质子转移途径被认为涉及表面组氨酸残基和一系列酸性残基和水分子。将通过改变质子转移途径中残基的环境和使用我们开发的方法测量质子转移速率来研究对质子转移重要的因素。用X射线结晶学和光谱技术，包括电子顺磁共振、电子核双共振和红外光谱技术，将研究具有改进的质子和电子转移速率的突变体的结构。这项拟议的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。功能分析、遗传信息和结构生物学的结合提供了对这些重要生物学过程的分子基础的理解，并应有助于为未来分子医学的发展奠定基础。

DESCRIPTION (provided by applicant): The proposed research is a study of electron and proton transfer reactions that are important for energy conversion processes in membrane proteins. The research is focused on the reaction of the bound ubiquinone QB in the photosynthetic reaction center (RC) from the bacterium Rhodobacter sphaeroides. 2e -+2H+ +QB -->QBH2. Site directed mutagenesis will be used to investigate the mechanism of proton-coupled electron transfer and the pathway and mechanism for proton transfer. The electron transfer rates for these reactions are complex and are believed to involve protein dynamics as well as proton 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 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 of these important biological processes and should help lay the foundations for future advances in molecular medicine.