Mechanism of Respiration and Energy Transduction

细胞色素bc1复合物是一种能量传递酶，参与细胞内的 在利用氧的真核细胞中呼吸，位于线粒体内部 膜的类似的bc1复合体位于许多细菌的质膜上， 它参与呼吸、反硝化、固氮和循环光合电子 转移，取决于物种。在所有这些生物体中，bc1复合物氧化 膜定位的醌醇和减少水溶性，c型细胞色素，并连接这一点， 电子转移反应，质子跨膜易位，其中BC1 复杂的居住。来自几个物种线粒体的bc1复合物已经被发现， 结晶和酶的机制，质子动力Q循环，是部分理解。 本研究的长期目标是了解细胞色素 bc1复合物，并阐明这种寡聚酶的亚基 复合物组装到线粒体内膜中。当前的具体目标 研究项目旨在回答以下有关该机制的问题。 - 泛醇氧化是协同反应还是顺序反应？ - 泛醇结合中负协同效应的结构基础是什么？ - 质子是如何传导到泛醌和泛醇反应位点的？ - 泛半醌的稳定性如何影响泛醌还原的速率？ 我们计划在酵母细胞色素bc1复合物中研究这些问题 酿酒酵母，因为这种酶可以通过分子遗传学方法进行修饰 并以足以进行生物化学和生物物理表征的量分离。

The cytochrome bc1 complex is an energy-transducing enzyme that participates in cell respiration in oxygen utilizing eukaryotic cells and is located in the inner mitochondrial membrane. A similar bc1 complex is located in the plasma membrane of many bacteria, where it takes part in respiration, denitrification, nitrogen fixation, and cyclic photosynthetic electron transfer, depending on the species. In all of these organisms the bc1 complex oxidizes a membrane-localized quinol and reduces a water-soluble, c-type cytochrome and links this electron transfer reaction to translocation of protons across the membrane in which the bc1 complex resides. The bc1 complexes from mitochondria of several species have been crystallized and the mechanism of the enzyme, the protonmotive Q cycle, is partly understood. The long term objectives of this research are to understand the mechanism of the cytochrome bc1 complex and to elucidate the pathway by which the subunits of this oligomeric enzyme complex are assembled into the inner mitochondrial membrane. The specific aims of the current research project are to answer the following questions regarding the mechanism. - Is ubiquinol oxidation a concerted or sequential reaction? - What is the structural basis of negative cooperativity in the binding of ubiquinol? - How are protons conducted to and from the ubiquinone and ubiquinol reaction sites? - How does ubisemiquinone stability affect the rate of ubiquinone reduction? We plan to investigate these questions in the cytochrome bc1 complex of the yeast Saccharomyces cerevisiae, since this enzyme can be modified by molecular genetics methods and isolated in quantities sufficient for biochemical and biophysical characterization.