Electron and Proton Transfer in Reaction Centers

描述（由申请人提供）：拟议的研究是对膜蛋白中能量转换过程重要的电子和质子转移反应的研究。研究了结合型泛醌QB在球形红细菌光合反应中心（RC）的反应。2e -+2H+ +QB --> QBH 2。定点突变将用于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，并且被认为涉及蛋白质动力学以及质子转移。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学过程的分子基础的理解，并且应该有助于为分子医学的未来进展奠定基础。

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.