Q-Band ENDOR (Electron Nuclear Double Resonance) of the High-Affinity Ubisemiquinone Center in Cytochrome bo3 from Escherichia coli
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...
Saved in:
Published in | Biochemistry (Easton) Vol. 39; no. 11; pp. 3169 - 3175 |
---|---|
Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
21.03.2000
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | 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. |
---|---|
Bibliography: | istex:87D3F4553E13E26277AC9818265AF6D642E724D3 Supported by the National Institutes of Health (Grant GM-35103 to C.P.S.) and by a grant from the U.S. Department of Energy (DEFGO2-87ER13716 to R.B.G.). ark:/67375/TPS-91BWN8JX-V ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-2960 1520-4995 |
DOI: | 10.1021/bi9926835 |