Membrane protein complexes can support both the generation and utilization of a transmembrane electrochemical proton potential (Δp), either by supporting transmembrane electron transfer coupled to protolytic reactions on opposite sides of the membrane or by supporting transmembrane proton transfer. Regarding the first mechanism, this has been unequivocally demonstrated to be operational for Δp-dependent catalysis of succinate oxidation by quinone in the case of the dihaem-containing SQR (succinate:menaquinone reductase) from the Gram-positive bacterium Bacillus licheniformis. This is physiologically relevant in that it allows the transmembrane Δp to drive the endergonic oxidation of succinate by menaquinone by the dihaem-containing SQR of Gram-positive bacteria. In the case of a related but different respiratory membrane protein complex, the dihaem-containing QFR (quinol:fumarate reductase) of the ϵ-proteobacterium Wolinella succinogenes, evidence has been obtained indicating that both mechanisms are combined, so as to facilitate transmembrane electron transfer by proton transfer via a both novel and essential compensatory transmembrane proton transfer pathway (‘E-pathway’). This is necessary because, although the reduction of fumarate by menaquinol is exergonic, it is obviously not exergonic enough to support the generation of a Δp. This compensatory E-pathway appears to be required by all dihaem-containing QFR enzymes and the conservation of the essential acidic residue on transmembrane helix V (Glu-C180 in W. succinogenes QFR) is a useful key for the sequence-based discrimination of these QFR enzymes from the dihaem-containing SQR enzymes.
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October 2008
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Conference Article|
September 19 2008
Electroneutral and electrogenic catalysis by dihaem-containing succinate:quinone oxidoreductases
C. Roy D. Lancaster;
C. Roy D. Lancaster
1
*Cluster of Excellence “Macromolecular Complexes”, Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
†Chair of Structural Biology, Saarland University, Faculty of Medicine, Building 60, D-66421 Homburg, Germany
1To whom correspondence should be addressed (email [email protected]).
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Elena Herzog;
Elena Herzog
*Cluster of Excellence “Macromolecular Complexes”, Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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Hanno D. Juhnke;
Hanno D. Juhnke
*Cluster of Excellence “Macromolecular Complexes”, Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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M. Gregor Madej;
M. Gregor Madej
2
*Cluster of Excellence “Macromolecular Complexes”, Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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Florian G. Müller;
Florian G. Müller
*Cluster of Excellence “Macromolecular Complexes”, Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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Rajsekhar Paul;
Rajsekhar Paul
*Cluster of Excellence “Macromolecular Complexes”, Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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Philipp G. Schleidt
Philipp G. Schleidt
*Cluster of Excellence “Macromolecular Complexes”, Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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Publisher: Portland Press Ltd
Received:
June 30 2008
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem Soc Trans (2008) 36 (5): 996–1000.
Article history
Received:
June 30 2008
Citation
C. Roy D. Lancaster, Elena Herzog, Hanno D. Juhnke, M. Gregor Madej, Florian G. Müller, Rajsekhar Paul, Philipp G. Schleidt; Electroneutral and electrogenic catalysis by dihaem-containing succinate:quinone oxidoreductases. Biochem Soc Trans 1 October 2008; 36 (5): 996–1000. doi: https://doi.org/10.1042/BST0360996
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