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Heme-copper terminal oxidase using both cytochrome c and ubiquinol as electron donors

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Gao,  Ye
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Peng,  Guohong
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society;
Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;

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Michel,  Hartmut
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Gao, Y., Meyer, B., Sokolova, L., Zwicker, K., Karas, M., Brutschy, B., et al. (2012). Heme-copper terminal oxidase using both cytochrome c and ubiquinol as electron donors. Proceedings of the National Academy of Sciences of the United States of America, 109(9), 3275-3280. doi:10.1073/pnas.1121040109.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-D57D-1
Abstract
The cytochrome c oxidase Cox2 has been purified from native membranes of the hyperthermophilic eubacterium Aquifex aeolicus. It is a cytochrome ba3 oxidase belonging to the family B of the heme-copper containing terminal oxidases. It consists of three subunits, subunit I (CoxA2, 63.9 kDa), subunit II (CoxB2, 16.8 kDa), and an additional subunit IIa of 5.2 kDa. Surprisingly it is able to oxidize both reduced cytochrome c and ubiquinol in a cyanide sensitive manner. Cox2 is part of a respiratory chain supercomplex. This supercomplex contains the fully assembled cytochrome bc1 complex and Cox2. Although direct ubiquinol oxidation by Cox2 conserves less energy than ubiquinol oxidation by the cytochrome bc1 complex followed by cytochrome c oxidation by a cytochrome c oxidase, ubiquinol oxidation by Cox2 is of advantage when all ubiquinone would be completely reduced to ubiquinol, e.g., by the sulfide∶quinone oxidoreductase, because the cytochrome bc1 complex requires the presence of ubiquinone to function according to the Q-cycle mechanism. In the case that all ubiquinone has been reduced to ubiquinol its reoxidation by Cox2 will enable the cytochrome bc1 complex to resume working.