Protonmotive pathways and mechanisms in the cytochrome bc 1 complex

@article{Hunte2003ProtonmotivePA,
  title={Protonmotive pathways and mechanisms in the cytochrome bc
1 complex},
  author={C. Hunte and H. Palsdottir and B. Trumpower},
  journal={FEBS Letters},
  year={2003},
  volume={545}
}
The cytochrome bc 1 complex catalyzes electron transfer from ubiquinol to cytochrome c by a protonmotive Q cycle mechanism in which electron transfer is linked to proton translocation across the inner mitochondrial membrane. In the Q cycle mechanism proton translocation is the net result of topographically segregated reduction of quinone and reoxidation of quinol on opposite sides of the membrane, with protons being carried across the membrane as hydrogens on the quinol. The linkage of proton… Expand
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TLDR
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References

SHOWING 1-10 OF 53 REFERENCES
The protonmotive Q cycle. Energy transduction by coupling of proton translocation to electron transfer by the cytochrome bc1 complex.
  • B. Trumpower
  • Chemistry, Medicine
  • The Journal of biological chemistry
  • 1990
TLDR
The purpose of this review is to explain the protonmotive Q cycle, one of the most important mechanisms of cellular energy transduction, found in a phylogenetically diverse range of organisms. Expand
Electron transfer by domain movement in cytochrome bc1
TLDR
X-ray crystal structures of the cytochrome bc1 complex from chicken, cow and rabbit in both the presence and absence of inhibitors of quinone oxidation, reveal two different locations for the extrinsic domain of one component of the enzyme, an iron–sulphur protein. Expand
Pathways for proton release during ubihydroquinone oxidation by the bc(1) complex.
  • A. Crofts, S. Hong, +4 authors E. Berry
  • Chemistry, Medicine
  • Proceedings of the National Academy of Sciences of the United States of America
  • 1999
TLDR
From the structure of the stigmatellin-containing mitochondrial complex, it is suggested that hydrogen bonds to the two quinol hydroxyl groups help to stabilize the enzyme-substrate complex and aid proton release and that the carboxylate function is essential for rapid turnover. Expand
A concerted, alternating sites mechanism of ubiquinol oxidation by the dimeric cytochrome bc(1) complex.
  • B. Trumpower
  • Chemistry, Medicine
  • Biochimica et biophysica acta
  • 2002
TLDR
A refinement of the protonmotive Q cycle mechanism is proposed in which oxidation of ubiquinol is a concerted reaction and occurs by an alternating, half-of-the-sites mechanism, which provides a raison d'être for the dimeric structure of the enzyme. Expand
Insights from the structure of the yeast cytochrome bc 1 complex: crystallization of membrane proteins with antibody fragments
  • C. Hunte
  • Chemistry, Medicine
  • FEBS letters
  • 2001
TLDR
Details of the catalytic sites of the ubiquinol:cytochrome c oxidoreductase complex, which are important for electron and proton transfer, are revealed. Expand
Possible molecular mechanisms of the protonmotive function of cytochrome systems.
  • P. Mitchell
  • Biology, Medicine
  • Journal of theoretical biology
  • 1976
TLDR
The newly introduced concepts of the protonmotive ubiquinone cycle, or Q cycle, and of the cyclic loop 2–3 system, which represent developments of the redox loop concept, are shown to provide a promising basis for the evolution of a satisfactory theory. Expand
Mitochondrial cytochrome b: evolution and structure of the protein.
TLDR
Comparison of inhibition titrations in combination with the analysis of the primary structures has enabled us to identify amino acid residues in cytochrome b that may be involved in the binding of the inhibitors and, by extrapolation, quinone/quinol. Expand
Steered molecular dynamics simulation of the Rieske subunit motion in the cytochrome bc(1) complex.
TLDR
Several metastable conformations of the ISP during its rotation were identified and the interactions stabilizing the initial, final, and intermediate positions of the soluble head of the Rieske iron-sulfur protein (ISP) domain were characterized. Expand
Biological electron transfer
TLDR
New results from the photosynthetic reaction center protein confirm that the electronic-tunneling medium appears relatively homogeneous, with any variances evident having no impact on function, and that control of intraprotein rates and directional specificity rests on a combination of distance, free energy, and reorganization energy. Expand
Role of protonatable groups of bovine heart bc(1) complex in ubiquinol binding and oxidation.
TLDR
The pH dependence of the initial reaction rate catalyzed by the isolated bovine heart ubiquinol-cytochrome c reductase (bc1 complex) varying decylbenzoquinol (DBH) and decylBenzoquinone (DB) concentrations was determined and the protonation of a group blocked catalysis, indicating its role in proton transfer. Expand
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