Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, D60438 Frankfurt, Germany.
Proc Natl Acad Sci U S A. 2011 Mar 8;108(10):3964-9. doi: 10.1073/pnas.1100950108. Epub 2011 Feb 22.
Cytochrome c oxidase (CcO) is the terminal enzyme of the respiratory chain. This redox-driven proton pump catalyzes the four-electron reduction of molecular oxygen to water, one of the most fundamental processes in biology. Elucidation of the intermediate structures in the catalytic cycle is crucial for understanding both the mechanism of oxygen reduction and its coupling to proton pumping. Using CcO from Paracoccus denitrificans, we demonstrate that the artificial F state, classically generated by reaction with an excess of hydrogen peroxide, can be converted into a new P state (in contradiction to the conventional direction of the catalytic cycle) by addition of ammonia at pH 9. We suggest that ammonia coordinates directly to Cu(B) in the binuclear active center in this P state and discuss the chemical structures of both oxoferryl intermediates F and P. Our results are compatible with a superoxide bound to Cu(B) in the F state.
细胞色素 c 氧化酶(CcO)是呼吸链的末端酶。这种氧化还原驱动的质子泵催化分子氧的四电子还原为水,这是生物学中最基本的过程之一。阐明催化循环中的中间结构对于理解氧还原的机制及其与质子泵的偶联至关重要。我们使用来自脱氮副球菌的 CcO 证明,通过在 pH 值为 9 时添加氨,可以将经典地通过与过量过氧化氢反应生成的人工 F 状态转化为新的 P 状态(与催化循环的传统方向相反)。我们建议在这种 P 状态下,氨直接与双核活性中心的 Cu(B)配位,并讨论了 oxoferryl 中间体 F 和 P 的化学结构。我们的结果与 F 状态下结合在 Cu(B)上的超氧化物一致。