PMID:10715139
| Citation |
Veselov, AV, Osborne, JP, Gennis, RB and Scholes, CP (2000) Q-band ENDOR (electron nuclear double resonance) of the high-affinity ubisemiquinone center in cytochrome bo3 from Escherichia coli. Biochemistry 39:3169-75 |
|---|---|
| Abstract |
Electron nuclear double resonance (ENDOR) was performed on the protein-bound, stabilized, high-affinity ubisemiquinone radical, QH*-, of bo3 quinol oxidase to determine its electronic spin distribution and to probe its interaction with its surroundings. Until this present work, such ENDOR studies of protein-stabilized ubisemiquinone centers have only been done on photosynthetic reaction centers whose function is to reduce a ubiquinol pool. In contrast, QH*- serves to oxidize a ubiquinol pool in the course of electron transfer from the ubiquinol pool to the oxygen-consuming center of terminal bo3 oxidase. As documented by large hyperfine couplings (>10 MHz) to nonexchangeable protons on the QH*- ubisemiquinone ring, we provide evidence for an electronic distribution on QH*- that is different from that of the semiquinones of reaction centers. Since the ubisemiquinone itself is physically nearly identical in both QH*- and the bacterial photosynthetic reaction centers, this electronic difference is evidently a function of the local protein environment. Interaction of QH*- with this local protein environment was explicitly shown by exchangeable deuteron ENDOR that implied hydrogen bonding to the quinone and by weak proton hyperfine couplings to the local protein matrix. |
| Links | |
| Keywords |
Benzoquinones/chemistry; Coenzymes; Cytochromes/chemistry; Deuterium; Electron Spin Resonance Spectroscopy/methods; Escherichia coli/enzymology; Escherichia coli Proteins; Protons; Ubiquinone/analogs & derivatives; Ubiquinone/chemistry |
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