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Active site of cytochrome cbb3
Virve Rauhamäki1, Dmitry A Bloch, Michael I Verkhovsky
1Helsinki Bioenergetics Group, Program for Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, P. O. Box 65 (Viikinkaari 1), 00014 Helsinki, Finland. virve.rauhamaki@helsinki.fi
The Journal of Biological Chemistry
|March 3, 2009
Summary
Cytochrome cbb(3) oxidases reduce oxygen to water, coupling electron transfer to proton pumping. Researchers studied Rhodobacter sphaeroides cytochrome cbb(3) redox centers and found a unique Glu-383 interaction crucial for enzyme function.
Area of Science:
- Biochemistry
- Molecular Biology
- Bioenergetics
Background:
- Cytochrome cbb(3) enzymes are vital heme-copper oxidases involved in cellular respiration.
- They catalyze oxygen reduction to water coupled with proton translocation across membranes.
Purpose of the Study:
- To investigate the thermodynamic properties of redox centers in Rhodobacter sphaeroides cytochrome cbb(3).
- To elucidate the structural and functional role of the Glu-383 residue near the active site heme b(3).
Main Methods:
- Optical and Electron Paramagnetic Resonance (EPR) spectroscopy were employed.
- Site-directed mutagenesis was used to probe the function of specific residues.
Main Results:
- Detailed redox potentials for five hemes and one copper ion were determined.
- Mutation of Glu-383 to glutamine significantly altered heme b(3) spectral properties and EPR symmetry, suggesting a role in hydrogen bonding.
- Mutation to aspartate had less pronounced effects, highlighting the specificity of the Glu-383 interaction.
Conclusions:
- The study reveals unique thermodynamic properties of Rhodobacter sphaeroides cytochrome cbb(3) redox centers.
- Glu-383 plays a critical role, likely through hydrogen bonding to the proximal histidine ligand of heme b(3), influencing enzyme structure and function.
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