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 对于初始光，诱导电子和质子转移反应 那将轻能转化为化学能。 一个关键组成部分 过程是结合的醌QB，它经历了反应Qb + 2e- + 2H+产生QBH2，将电子转移与质子摄取 解决方案。该反应是质子泵的第一步 使用光能在整个细胞膜上的质子。 一个主要的未得到答复 问题涉及将电子转移到QB的机制。 最近的结果表明，第一和第二电子 向QB转移分别由蛋白质动力学和 质子平衡。 这些机制将通过更改来研究 使用站点定向突变附近的残留物，并利用新颖 改变喹酮电子传输的驱动力的技术 替换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 质子转移到QB的途径。 最近的结构工作强烈 提出了内部水分子在质子途径中的作用 从蛋白质表面转移到附近蛋白质的内部 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 质子转移到QB站点。 这些突变对质子的影响 将使用测量质子速率的测定法监测转移 在蛋白质中转移。 这些研究特别有趣 对于其他膜蛋白的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 催化质子耦合的电子工艺。 RC的研究可以 帮助我们理解这一重要阶层 蛋白质。