QUINONE BINDING SITES IN BACTERIAL REACTION CENTERS

细菌反应中心的醌结合位点

• 批准号: 3299924
• 负责人: MELVIN Y OKAMURA
• 金额: $ 16.82万
• 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 1994-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3299924
• 关键词: aminoacid; chemical binding; electrical potential; electron transport; herbicides; hydrogen transport; membrane permeability; membrane potentials; membrane proteins; protein transport; quinones; site directed mutagenesis

The bacterial reaction center (RC) is a membrane bound protein that plays the central role in the conversion lectromagnetic radiation into chemical energy. The RC catalyzes the light driven electron transfer from cytochrome c2 to a quinone-Fe complex, that contains a primary quinone QA and a secondary quinone QB. The primary quinone QA, plays an important role in the initial electron transfer step. The secondary quinone QB plays a central role in the electron and proteon translocation process, acting as a two electron two proton acceptor species which is involved in the primary step of proton translocation. This proposal addresses the question of the molecular basis for the function of the quinones using the technique of site directed mutagenesis in the bacterium Rb. sphaeroides. By modifying amino acid residues near the Q binding sites and measuring the concomitant changes in activity we will identify the residues involved in the following functions: a) Quinone and herbicide binding. Residues near the quinone binding sites will be modified and the binding constants of quinone and herbicide will be determined. The results will give information about the nature of substrate and inhibitor binding and the mechanism of herbicide resistance. b) Electron transfer kinetics. Aromatic and charged amino acids will be modified and their effects on electron tyransfer determined. The results should give information about the mechanisms of electron transfer. c) Electrostatic stabilization of QQ -. Charged amino acid residues will be modified and the equilibrium between Q-A QB and QAQ-B will be determined. The results should give information about the electrostatic interactions in a membrane protein. d) Proton transport to QB. Protonable residues which can potentialy form a proton transfer chain from the RC surface to the QB site will be modified and their effect on the rate of proton transfer will be detemined. The results should test the mechanism of proton transport in biological membranes.

细菌反应中心（RC）是一种膜结合蛋白， 在电磁辐射的转换中起着核心作用 转化为化学能。 RC催化光驱动电子 从细胞色素c2转移到醌-Fe络合物，其含有 伯醌QA和仲醌QB。 主 醌QA，在初始电子中起重要作用 转移步骤。 仲醌QB在以下方面起着核心作用： 电子和蛋白质易位过程，作为两个 电子2质子受体物种，这是参与 质子转移的第一步。 该提案针对 醌类功能的分子基础问题 使用细菌中的定点诱变技术， RB. sphaeroides 通过修饰Q附近的氨基酸残基 结合位点和测量伴随的活性变化， 将确定参与以下功能的残基： a）醌和除草剂结合。 醌附近的残留物 结合位点将被修改，醌的结合常数 并确定除草剂。 结果将给出 有关底物和抑制剂结合性质的信息， 除草剂抗性的机制。 B）电子转移动力学。 芳香族和带电氨基酸 以及它们对电子转移的影响 测定 结果应提供有关 电子转移的机制。 c）QQ -的静电稳定。 电荷的氨基酸 残基将被修饰，Q-A QB和 将确定QAQ-B。 结果应该提供信息 关于膜蛋白中的静电相互作用。 d）质子运输到QB。 可质子化的残基， 潜在地形成从RC表面到表面的质子转移链。 QB位点的修饰及其对质子化速率的影响 转移将被确定。 结果应该测试机制 质子在生物膜中的传输。