MOLECULAR ARCHITECTURE OF UQH2: CYTC2 OXIDOREDUCTASE

UQH2 的分子结构：CYTC2 氧化还原酶

• 批准号: 6342797
• 负责人: ANTONY R. CROFTS
• 金额: $ 24.76万
• 依托单位: UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 2003-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6342797
• 关键词: NADPH cytochrome c2 reductase; Rhodospirillales; X ray crystallography; active sites; bioenergetics; circular dichroism; cytochrome b; dimer; electron spin resonance spectroscopy; electron transport; enzyme activity; enzyme complex; enzyme inhibitors; enzyme mechanism; enzyme structure; enzyme substrate complex; hydroquinones; iron sulfur protein; photosynthesis; photosynthetic bacteria; protein structure function; site directed mutagenesis; structural biology; ubiquinone; ultracentrifugation

The enzymes of the bc1 complex family (ubiquinol:cytochrome c oxidoreductases, and the closely related b6f complex of oxygenic photosynthesis), carry the energy flux of the biosphere, serving as the central enzymes of respiratory and photosynthetic electron transfer chains. The aim of this project has been to understand how these important enzymes function. X-ray crystallographic structures for several mitochondrial complexes have recently been solved in collaboration with Dr. Ed Berry, and an extensive analysis in the light of previous work has provide new insights on function. Much biophysical work has established the basic mechanism, and the focus in recent years has been on putting this into a structural context. The complexes catalyze the oxidation of ubiquinol and the reduction of cytochrome c through a modified Q-cycle. Three catalytic subunits, a cytochrome b with two hemes, cytochrome c1 and an iron sulfur protein, house the mechanism. These are well conserved across the bacterial/mitochondrial divide. Two separate internal electron transfer chains connect three catalytic sites that catalyze oxidation and reduction of the quinone pool, and reduction of cytochrome c. Electron transfer across the membrane, and coupling of these redox reactions to the release or uptake of protons, allows the complex to generate the transmembrane gradient that drives ATP synthesis. From our analysis of the structure, we have suggested some novel extensions of this basic mechanism, including a dramatic movement of the iron sulfur protein between its two reaction partners, a revised mechanism for the reaction by which quinol is oxidized, and a more detailed understanding of the quinone reduction site. In the renewal period, we will make use of the structure in an extended exploration of the molecular mechanism, using spectroscopic methods, and biophysical, molecular engineering and biochemical protocols developed under the grant. Apart from its intrinsic interest, the bc1 complex is a major site of production of oxygen radicals, which cause cell aging and DNA damage leading to cancer, and also the locus of inherited genetic diseases. Natural inhibitors block turnover by mimicking quinone at the catalytic sites, and commercial interest has centered on the possibility of using these as green pesticides.

bc1复合物家族的酶（泛醇：细胞色素c氧化还原酶，以及与氧光合作用密切相关的b6f复合物）携带着生物圈的能量流，作为呼吸和光合作用电子传递链的中心酶。 该项目的目的是了解这些重要的酶如何发挥作用。 最近与 Ed Berry 博士合作解决了几种线粒体复合物的 X 射线晶体结构，并且根据之前的工作进行了广泛的分析，提供了关于功能的新见解。 许多生物物理学工作已经建立了基本机制，近年来的重点是将其纳入结构背景。 该复合物通过改良的 Q 循环催化泛醇的氧化和细胞色素 c 的还原。 该机制由三个催化亚基组成，即带有两个血红素的细胞色素 b、细胞色素 c1 和铁硫蛋白。 这些在细菌/线粒体鸿沟中得到了很好的保守。 两条独立的内部电子转移链连接三个催化位点，催化醌池的氧化和还原，以及细胞色素 c 的还原。 电子跨膜转移，以及这些氧化还原反应与质子的释放或摄取的耦合，使得复合物能够产生驱动 ATP 合成的跨膜梯度。 通过对结构的分析，我们提出了这一基本机制的一些新的扩展，包括铁硫蛋白在其两个反应伙伴之间的戏剧性运动、对醌氧化反应的修订机制以及更详细的理解醌还原位点。 在更新期间，我们将利用该结构，利用光谱方法以及在资助下开发的生物物理、分子工程和生化方案，对分子机制进行扩展探索。 除了其固有的兴趣外，bc1复合体还是氧自由基的主要产生位点，氧自由基会导致细胞老化和DNA损伤，从而导致癌症，也是遗传性疾病的发生地。天然抑制剂通过在催化位点模仿醌来阻止转化，商业兴趣集中在将它们用作绿色农药的可能性上。