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Probing heart cytochrome c oxidase structure and function by infrared spectroscopy
W S Caughey1, A Dong, V Sampath
1Department of Biochemistry, Colorado State University, Fort Collins 80523.
Journal of Bioenergetics and Biomembranes
|April 1, 1993
Summary
Infrared (IR) spectroscopy reveals how carbon monoxide and cyanide bind to bovine heart cytochrome c oxidase. These findings link enzyme structure, redox state, and activity, offering insights into oxygen reduction and proton pumping.
Area of Science:
- Biochemistry
- Spectroscopy
- Enzymology
Background:
- Cytochrome c oxidase is a crucial enzyme in cellular respiration.
- Understanding its structure-function relationship is key to elucidating oxygen reduction and proton pumping mechanisms.
Purpose of the Study:
- To investigate the binding of small molecules (CO, CN-, N2O) to bovine heart cytochrome c oxidase using IR spectroscopy.
- To correlate spectral data with enzyme redox states, conformation, and activity.
Main Methods:
- Fourier Transform Infrared (FTIR) spectroscopy was employed to analyze vibrational modes of cytochrome c oxidase.
- Specific IR spectra (C-O, C-N, Amide I, N2O) were measured under varying conditions (redox state, pH, anesthetics).
Main Results:
- CO binding occurs in two distinct conformers, sensitive to Fea and CuA oxidation states but not pH or anesthetics.
- Cyanide binding reveals three different structures that vary with enzyme redox level, indicating dynamic electron exchange.
- Amide I bands show high alpha-helix content with subtle changes related to redox state and anesthetics.
- N2O binding sites were identified, correlating with partial enzyme inhibition.
Conclusions:
- IR spectroscopy provides quantitative and qualitative insights into cytochrome c oxidase structure and reactions.
- Redox-dependent conformational changes and electron transfer dynamics are reflected in ligand binding and spectral properties.
- Anesthetic molecules interact with specific sites within the enzyme, affecting its function.