Light-induced structural changes in cytochrome c oxidase : Measurements of electrogenic events and absorbance changes

• Published in: FEBS letters Vol. 318; no. 2; pp. 134 - 138
• Main Authors: Hallén, Stefan, Oliveberg, Mikael, Brzezinski, Peter
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-1993; Elsevier
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cattle; Cytochrome c oxidase; Electron gating; Electron transfer; Electron Transport Complex IV - metabolism; Electron Transport Complex IV - physiology; Electron Transport Complex IV - radiation effects; Enzymes and enzyme inhibitors; Flash photolysis; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Ligand; Light; Membrane Potentials; Nitrogen; Oxidation-Reduction; Oxidoreductases; Spectrum Analysis; Cytochrome c oxidase; EC 1.9.3.1; Ligand; Electron gating; Electron transfer; cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase; Flash photolysis; COX; Ligand binding; Enzyme; Phospholipid; Structure modification
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(93)80007-H

We have investigated flash-induced electrogenic events and absorbance changes in cytochrome
c oxidase in the absence of dioxygen and carbon monoxide. Electrogenic events were studied using a Teflon-bound layer of cytochrome
c oxidase oriented in a phospholipid monolayer. Absorbance changes were observed exclusively in partly reduced cytochrome
c oxidase; the largest changes were found in the one-electron-reduced species. Electrogenic events were detected in all reduction states of the enzyme. Both types of experiments displayed a rapid (< 0.5 μ;s) event followed by a biphasic relaxation. The time constants of the relaxation were 6 ± 2 μ;s and 70 ± 10 μ;s in the electrogenicity, and 9 ± 3 μ;s and 81 ± 6 μ;s in the absorbance changes (at ~22 °C). The kinetic absorbance difference spectrum was consistent with that of reduced minus oxidized haem. The experimental results are discussed in terms of structural changes in the vicinity of cytochrome
a
3. These changes may play an important role in all studies that involve flash photolysis of cytochrome
c oxidase-ligand complexes.