ELECTRON AND PROTON TRANSFER IN REACTION CENTERS

反应中心的电子和质子转移

• 批准号: 6125417
• 负责人: MELVIN Y OKAMURA
• 金额: $ 26.43万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-04-01 至 2002-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6125417
• 关键词: Raman spectrometry; Rhodopseudomonas; X ray crystallography; binding sites; bioenergetics; chemical binding; chemical kinetics; cytochrome oxidase; electron transport; hydrogen transport; infrared spectrometry; membrane proteins; nuclear magnetic resonance spectroscopy; oxidation reduction reaction; photosynthetic reaction centers; protein structure function; site directed mutagenesis; ubiquinone; water

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.

细菌反应中心（RC）是负责的膜蛋白 因为初始光引发电子和质子转移反应 将光能转化为化学能。 其中一个关键组成部分 过程是结合的醌 QB，它发生反应 QB + 2e- + 2H+ 产生 QBH2，将电子转移与质子吸收耦合 解决方案。该反应是驱动质子泵的第一步 利用光能使质子穿过细胞膜。 主要未答复 问题涉及电子转移到 QB 的机制。 最近的结果表明第一和第二电子 到 QB 的转移分别由蛋白质动力学和 质子化平衡。 这些机制将通过改变来研究 使用定点突变，并利用一种新的方法，在 QB 附近的残基上进行 改变醌电子转移驱动力的技术 取代以确定电子的速率限制步骤 转移过程。 第二个主要问题涉及机制和 质子转移至 QB 的途径。 最近的结构工作强烈 表明内部水分子在质子路径中的作用 从蛋白质表面转移到蛋白质内部附近 QB。 这些水分子的作用将通过突变来检查 与关键水分子相关的蛋白质残基可以阻断 质子转移到 QB 位点。 这些突变对质子的影响 将使用测量质子速率的测定来监测转移 转移到蛋白质中。 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 复合物 催化质子耦合电子过程。对RC的研究可以 有助于我们理解这一重要类别 蛋白质。