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

Gao, Ye; Meyer, Björn; Sokolova, Lucie; Zwicker, Klaus; Karas, Michael; Brutschy, Bernd; Peng, Guohong; Michel, Hartmut

doi:10.1073/pnas.1121040109

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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: https://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.