Membrane protein complexes can support both the generation and utilisation of a transmembrane electrochemical proton potential ('proton-motive force'), either by transmembrane electron transfer coupled to protolytic reactions on opposite sides of the membrane or by transmembrane proton transfer ...
Membrane protein complexes can support both the generation and utilisation of a transmembrane electrochemical proton potential ('proton-motive force'), either by transmembrane electron transfer coupled to protolytic reactions on opposite sides of the membrane or by transmembrane proton transfer. Here we provide the first evidence that both of these mechanisms are combined in the case of a specific respiratory membrane protein complex, the dihaem-containing quinol:fumarate reductase (QFR) of Wolinella succinogenes, so as to facilitate transmembrane electron transfer by transmembrane proton transfer. We also demonstrate the non-functionality of this novel transmembrane proton transfer pathway ('E-pathway') in a variant QFR where a key glutamate residue has been replaced. The 'E-pathway', discussed on the basis of the 1.78-Angstrom-resolution crystal structure of QFR, can be concluded to be essential also for the viability of pathogenic epsilon-proteobacteria such as Helicobacter pylori and is possibly relevant to proton transfer in other dihaem-containing membrane proteins, performing very different physiological functions.
Related Citations:
Wolinella Succinogenes Quinol:Fumarate Reductase -2.2 Angstrom Resolution Crystal Structure and the E-Pathway Hypothesis of Coupled Transmembrane Proton and Electron Transfer Lancaster, C.R.D. (2002) Biochim Biophys Acta 1565: 215
A Third Crystal Form of Wolinella Succinogenes Quinol:Fumarate Reductase Reveals Domain Closure at the Site of Fumarate Reduction Lancaster, C.R.D., Gross, R., Simon, J. (2001) Eur J Biochem 268: 1820
Essential Role of Glu-C66 for Menaquinol Oxidation Indicates Transmembrane Electrochemical Potential Generation by Wolinella Succinogenes Fumarate Reductase Lancaster, C.R.D., Gross, R., Haas, A., Ritter, M., Maentele, W., Simon, J., Kroeger, A. (2000) Proc Natl Acad Sci U S A 97: 13051
Structure of Fumarate Reductase from Wolinella Succinogenes at 2.2 Angstroms Resolution Lancaster, C.R.D., Kroeger, A., Auer, M., Michel, H. (1999) Nature 402: 377
Organizational Affiliation:
Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
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