ELECTRON AND PROTON TRANSFER IN REACTION CENTERS

细菌反应中心(RC)是负责膜蛋白的 因为最初的光会引起电子和质子转移反应 将光能转化为化学能。这其中的一个关键组成部分 过程是结合的苯二酚，它经历反应QB+2E- +2H+产生QBH2，耦合电子转移和质子吸收 解决方案。这个反应是驱动质子泵的第一步。 利用光能使质子穿过细胞膜。一个未获答复的重大问题 这个问题涉及到电子转移到QB的机制。 最近的结果表明，第一个和第二个电子 转移到QB分别由蛋白质动力学和蛋白质动力学决定 质子化平衡。这些机制将通过改变 QB附近的残基使用定点突变并利用一种新的 利用苯二酚改变电子转移驱动力的技术 确定电子的速率限制步骤的代换 转移过程。第二个主要问题涉及机制和 质子转移到QB的途径。最近的结构工作已经很强劲了 暗示了内部水分子在质子途径中的作用 从蛋白质表面转移到蛋白质内部 QB。这些水分子的作用将通过突变来检验 与关键水分子相关的蛋白质残留物需要阻止 质子转移到QB位置。这些突变对质子的影响 将使用测量质子速率的分析来监测转移 把蛋白质转移进来。这些研究特别有趣，因为 其他膜蛋白结构研究的最新进展 包括细胞色素氧化酶和细胞色素Bc1复合体 催化质子耦合电子过程。关于RC的研究可以 有助于帮助我们理解这一重要的课程 蛋白质。

The bacterial reaction center (RC) is the membrane protein responsible for the initial light induces electron and proton transfer reactions that convert light energy into chemical energy. A key component of this process is the bound quinone, QB, which undergoes the reaction QB + 2e- + 2H+ yields QBH2, coupling electron transfer with proton uptake from solution. This reaction is the first step in the proton pump that drives protons across the cell membrane using light energy. A major unanswered question involves the mechanisms for the transfer of electrons to QB. Recent results have indicated that the first and second electron transfers to QB are respectively dictated by protein dynamics and protonation equilibria. These mechanisms will be studied by changing residues near QB using site directed mutations, and by utilizing a novel technique for varying the driving force for electron transfer by quinone substitution to determine the rate limiting step for the electron transfer process. A second major question involves the mechanism and pathway for proton transfer to QB. Recent structural work has strongly suggested the role of internal water molecules in the pathway for proton transfer from the protein surface into the interior of the protein near QB. The role of these water molecules will be examined by mutation of protein residues associated with critical water molecules to block proton transfer to the QB site. The effect of these mutations on proton transfer will be monitored using assays for measuring the rate of proton transfer in the protein. These studies are particularly interesting due to recent advances in structural studies of other membrane proteins including Cytochrome Oxidase and the Cytochrome bc1 Complex that also catalyze proton-coupled electron processes. The studies on the RC can help to contribute to our understanding of this important class of proteins.