Mechanism of Respiration and Energy Transduction

细胞色素bc1复合体是一种参与细胞内的能量转导酶。 利用真核细胞的氧气呼吸作用，位于线粒体内部 薄膜。许多细菌的质膜中都有一个类似的Bc1复合体，其中 它参与呼吸作用、反硝化作用、固氮作用和循环光合作用电子。 根据物种的不同进行转移。在所有这些生物中，Bc1复合体氧化一个 膜上定位的喹酚，减少了一种水溶性的c型细胞色素，并连接到这个 电子转移反应使质子转移通过Bc1的膜 复杂的居住环境。几个物种线粒体的Bc1复合体已经被 结晶和酶的机制，即质子动力Q循环，是部分了解。 本研究的长期目标是了解细胞色素的作用机制。 Bc1复合体，并阐明这种寡聚体酶的亚基 复合体组装成线粒体膜。当前的具体目标 研究项目将回答以下关于该机制的问题。 -泛喹酚氧化是协同反应还是顺序反应？ -泛喹酚结合中负协作性的结构基础是什么？ -质子如何传入和传出泛醌和泛喹酚反应点？ --辅酶Q稳定性如何影响辅酶Q还原的速度？ 我们计划在酵母的细胞色素bc1复合体中研究这些问题。 酿酒酵母，因为这种酶可以通过分子遗传学方法进行修饰 并分离出足以进行生化和生物物理鉴定的数量。

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.