PMID:11170426
| Citation |
Grimaldi, S, MacMillan, F, Ostermann, T, Ludwig, B, Michel, H and Prisner, T (2001) QH*- ubisemiquinone radical in the bo3-type ubiquinol oxidase studied by pulsed electron paramagnetic resonance and hyperfine sublevel correlation spectroscopy. Biochemistry 40:1037-43 |
|---|---|
| Abstract |
The high-affinity QH ubiquinone-binding site in the bo(3) ubiquinol oxidase from Escherichia coli has been characterized by an investigation of the native ubiquinone radical anion QH(*-) by pulsed electron paramagnetic resonance (EPR) spectroscopy. One- and two-dimensional electron spin-echo envelope modulation (ESEEM) spectra reveal strong interactions of the unpaired electron of QH(*-) with a nitrogen nucleus from the surrounding protein matrix. From analysis of the experimental data, the (14)N nuclear quadrupolar parameters have been determined: kappa = e(2)qQ/4h = 0.93 MHz and eta = 0.50. This assignment is confirmed by hyperfine sublevel correlation (HYSCORE) spectroscopy. On the basis of a comparison of these data with those obtained previously for other membrane-protein bound semiquinone radicals and model systems, this nucleus is assigned to a protein backbone nitrogen. This result is discussed with regard to the location and potential function of QH in the enzyme. |
| Links | |
| Keywords |
Anions; Coenzymes; Cytochromes/chemistry; Electron Spin Resonance Spectroscopy; Electron Transport Complex IV/chemistry; Escherichia coli/enzymology; Escherichia coli Proteins; Free Radicals/chemistry; Magnetic Resonance Spectroscopy; Ubiquinone/analogs & derivatives; Ubiquinone/chemistry |
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