Publications

• The structure of the ubiquinol oxidase from Escherichia coli and its ubiquinone binding site.

  Abramson J., Riistama S., Larsson G., Jasaitis A., Svensson-Ek M., Puustinen A., Iwata S., Wikstrom M.

  Cell respiration is catalyzed by the heme-copper oxidase superfamily of enzymes, which comprises cytochrome c and ubiquinol oxidases. These membrane proteins utilize different electron donors through dissimilar access mechanisms. We report here the first structure of a ubiquinol oxidase, cytochrom ... >> More

  Cell respiration is catalyzed by the heme-copper oxidase superfamily of enzymes, which comprises cytochrome c and ubiquinol oxidases. These membrane proteins utilize different electron donors through dissimilar access mechanisms. We report here the first structure of a ubiquinol oxidase, cytochrome bo3, from Escherichia coli. The overall structure of the enzyme is similar to those of cytochrome c oxidases; however, the membrane-spanning region of subunit I contains a cluster of polar residues exposed to the interior of the lipid bilayer that is not present in the cytochrome c oxidase. Mutagenesis studies on these residues strongly suggest that this region forms a quinone binding site. A sequence comparison of this region with known quinone binding sites in other membrane proteins shows remarkable similarities. In light of these findings we suggest specific roles for these polar residues in electron and proton transfer in ubiquinol oxidase. << Less

  Nat. Struct. Biol. 7:910-917(2000) [PubMed] [EuropePMC]

• Time-resolved electrometric and optical studies on cytochrome bd suggest a mechanism of electron-proton coupling in the di-heme active site.

  Belevich I., Borisov V.B., Zhang J., Yang K., Konstantinov A.A., Gennis R.B., Verkhovsky M.I.

  Time-resolved electron transfer and electrogenic H(+) translocation have been compared in a bd-type quinol oxidase from Escherichia coli and its E445A mutant. The high-spin heme b(595) is found to be retained by the enzyme in contrast to the original proposal, but it is not reducible even by exces ... >> More

  Time-resolved electron transfer and electrogenic H(+) translocation have been compared in a bd-type quinol oxidase from Escherichia coli and its E445A mutant. The high-spin heme b(595) is found to be retained by the enzyme in contrast to the original proposal, but it is not reducible even by excess of dithionite. When preincubated with the reductants, both the WT (b(558)(2+), b(595)(2+), d(2+)) and E445A mutant oxidase (b(558)(2+), b(595)(3+), d(2+)) bind O(2) rapidly, but formation of the oxoferryl state in the mutant is approximately 100-fold slower than in the WT enzyme. At the same time, the E445A substitution does not affect intraprotein electron re-equilibration after the photolysis of CO bound to ferrous heme d in the one-electron-reduced enzyme (the so-called "electron backflow"). The backflow is coupled to membrane potential generation. Electron transfer between hemes d and b(558) is electrogenic. In contrast, electron transfer between hemes d and b(595) is not electrogenic, although heme b(595) is the major electron acceptor for heme d during the backflow, and therefore is not likely to be accompanied by net H(+) uptake or release. The E445A replacement does not alter electron distribution between hemes b(595) and d in the one-electron reduced cytochrome bd [E(m)(d) > E(m)(b(595)), where E(m) is the midpoint redox potential]; however, it precludes reduction of heme b(595), given heme d has been reduced already by the first electron. Presumably, E445 is one of the two redox-linked ionizable groups required for charge compensation of the di-heme oxygen-reducing site (b(595), d) upon its full reduction by two electrons. << Less

  Proc Natl Acad Sci U S A 102:3657-3662(2005) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.