MOLECULAR ARCHITECTURE OF UQH2: CYTC2 OXIDOREDUCTASE

Bc1复合体家族的酶(泛喹酚：细胞色素c氧化还原酶，以及与之密切相关的氧合光合作用的b6f复合体)携带生物圈的能量流，是呼吸和光合作用电子传递链的中心酶。这个项目的目的是了解这些重要的酶是如何发挥作用的。最近与埃德·贝里博士合作，解决了几个线粒体复合体的X射线晶体结构，结合以前的工作进行了广泛的分析，为功能提供了新的见解。许多生物物理工作已经建立了基本机制，近年来的重点一直是将其置于结构背景下。该配合物通过一个修饰的Q环催化泛喹酚的氧化和细胞色素c的还原。三个催化亚基，一个含有两个血红素的细胞色素b，一个细胞色素c1和一个铁硫蛋白，包含了这个机制。它们在细菌/线粒体分裂中被很好地保守。两个独立的内部电子转移链连接三个催化部位，催化苯醌的氧化和还原，细胞色素c的还原。跨膜的电子转移，以及这些氧化还原反应与质子的释放或吸收的耦合，允许复合体产生驱动ATP合成的跨膜梯度。从我们对结构的分析中，我们提出了这一基本机理的一些新的扩展，包括铁硫蛋白在其两个反应伙伴之间的戏剧性移动，对苯二酚被氧化的反应机理的修正，以及对苯醌还原位置的更详细的理解。在更新期，我们将利用这种结构，利用光谱学方法，以及在赠款下开发的生物物理、分子工程和生物化学方案，对分子机制进行扩展探索。除了其内在的兴趣，Bc1复合体是产生氧自由基的主要部位，氧自由基导致细胞衰老和DNA损伤导致癌症，也是遗传性疾病的场所。天然抑制剂通过在催化部位模拟苯醌来阻止周转，商业兴趣集中在将这些用作绿色杀虫剂的可能性上。

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.