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Proton uptake controls electron transfer in cytochrome c oxidase
M Karpefors1, P Adelroth, Y Zhen
1Department of Biochemistry and Biophysics, Göteborg University, (Medicinaregatan 9C) P.O. Box 462, SE-405 30 Göteborg, Sweden.
Summary
Proton uptake controls electron transfer in cytochrome c oxidase, ensuring tight coupling for proton pumping. This mechanism prevents premature electron transfer, vital for efficient energy conversion.
Area of Science:
- Biochemistry
- Bioenergetics
- Enzyme kinetics
Background:
- Cytochrome c oxidase couples electron transfer to proton pumping.
- Proton uptake is essential for efficient enzyme function.
- The interplay between electron and proton transfer rates is crucial.
Purpose of the Study:
- To investigate whether proton uptake controls electron transfer or vice versa in cytochrome c oxidase.
- To elucidate the mechanism coupling electron transfer to proton pumping.
Main Methods:
- Site-specific mutagenesis of Rhodobacter sphaeroides cytochrome c oxidase (M263L mutant).
- Kinetic analysis of electron transfer and proton uptake rates.
- Comparison with wild-type and EQ(I-286) mutant enzymes.
Main Results:
- The M263L mutation increased the redox potential of CuA but did not alter proton uptake rate.
- Electron transfer from CuA to heme a was impaired in the M263L mutant.
- Results confirmed that proton uptake controls CuA --> heme a electron transfer.
Conclusions:
- Proton uptake is the rate-limiting step for electron transfer from CuA to heme a.
- This control mechanism ensures tight coupling between electron transfer and proton pumping.
- The findings clarify a key aspect of respiratory energy transduction.