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Review
. 2003 Feb 4;100(3):773-5.
doi: 10.1073/pnas.0330050100. Epub 2003 Jan 27.

The dichotomy of complex I: a sodium ion pump or a proton pump

Judy Hirst  1
Affiliations
Review

The dichotomy of complex I: a sodium ion pump or a proton pump

Judy Hirst. Proc Natl Acad Sci U S A. .
No abstract available

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Figures

Figure 1
Figure 1
The quinone/semiquinone redox pump. (1) Reduction of the quinone causes protonation from the matrix side; (2) a conformational change exposes the semiquinone to the intermembrane space; and (3) oxidation of the semiquinone causes proton expulsion to the intermembrane space. The energy required to pump the proton across the membrane is provided by a decrease in the potential energy of the electron.
Figure 2
Figure 2
Proton translocation across a hydrophobic barrier in response to the reduction of iron–sulfur cluster N2, mediated by a carboxylate residue. (1) Reduction of cluster N2; (2) the increased pK of the carboxylate causes it to collect a proton from the solvent channel; (3) the carboxylic acid group carries the proton across the hydrophobic barrier to the cluster; and (4) proton transfer from the carboxylic acid to the cluster (or a nearby group) that has a high pK in the reduced state.
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