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Inner Mitochondrial Membrane Sensitivity to Na+ Reveals Partially Segmented Functional CoQ Pools

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Variable proton-pumping stoichiometry in structural variants of cytochrome c oxidase.

Peter Brzezinski¹, Ann-Louise Johansson

¹Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden. peterb@dbb.su.se

Biochimica Et Biophysica Acta

|February 27, 2010

Summary

Studies on uncoupled cytochrome c oxidase variants reveal altered glutamate residue pKa values, linking structural changes to uncoupled proton pumping during oxygen reduction.

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Area of Science:

Biochemistry
Molecular Biology
Bioenergetics

Background:

Cytochrome c oxidase (CytcO) is a membrane-bound enzyme crucial for cellular respiration, coupling oxygen reduction to proton pumping.
Understanding the mechanism of proton pumping is vital for comprehending energy conservation in cells.
Uncoupled CytcO variants offer insights into the structure-function relationship of proton translocation.

Purpose of the Study:

To investigate the molecular mechanisms underlying proton pumping in cytochrome c oxidase.
To explore the role of a specific glutamate residue's pKa in coupling O2 reduction to proton translocation.
To link structural modifications in CytcO variants to altered proton pumping efficiency.

Main Methods:

Comparative analysis of wild-type and uncoupled cytochrome c oxidase variants.
Characterization of structural changes and their impact on enzyme kinetics.
Investigation of the apparent pKa of key glutamate residues within proton pathways.

Main Results:

Uncoupled CytcO variants exhibit altered pKa values for a deep-located glutamate residue.
These pKa shifts correlate with changes in the local structural environment near the catalytic site.
The observed pKa modulations are linked to the uncoupling of proton pumping from oxygen reduction.

Conclusions:

Structural alterations in CytcO significantly impact the proton transfer pathway.
Modulation of glutamate pKa is a key factor in uncoupling proton pumping from O2 reduction.
This study provides a quantitative link between structural changes, pKa modulation, and the loss of proton pumping efficiency.