Electron paramagnetic resonance studies of succinate:ubiquinone oxidoreductase from Paracoccus denitrificans : Evidence for a magnetic interaction between the 3Fe-4S cluster and cytochrome b
(1997) In Journal of Biological Chemistry- Abstract
- Electron paramagnetic resonance (EPR) studies of succinate:ubiquinone oxidoreductase (SQR) from Paracoccus denitrificans have been undertaken in the purified and membrane-bound states, Spectroscopic ''signatures'' accounting for the three iron-sulfur clusters (2Fe-2S, 3Fe-4S, and 4Fe-4S), cytochrome b, flavin, and protein-bound ubisemiquinone radicals have been obtained in air-oxidized, succinate-reduced, and dithionite-reduced preparations at 4-10 K. Spectra obtained at 170 K in the presence of excess succinate showed a signal typical of that of a flavin radical, but superimposed with another signal. The superimposed signal originated from two bound ubisemiquinones, as shown by spectral simulations, Power saturation measurements performed... (More)
- Electron paramagnetic resonance (EPR) studies of succinate:ubiquinone oxidoreductase (SQR) from Paracoccus denitrificans have been undertaken in the purified and membrane-bound states, Spectroscopic ''signatures'' accounting for the three iron-sulfur clusters (2Fe-2S, 3Fe-4S, and 4Fe-4S), cytochrome b, flavin, and protein-bound ubisemiquinone radicals have been obtained in air-oxidized, succinate-reduced, and dithionite-reduced preparations at 4-10 K. Spectra obtained at 170 K in the presence of excess succinate showed a signal typical of that of a flavin radical, but superimposed with another signal. The superimposed signal originated from two bound ubisemiquinones, as shown by spectral simulations, Power saturation measurements performed on the air-oxidized enzyme provided evidence for a weak magnetic dipolar interaction operating between the oxidized 3Fe-4S cluster and the oxidized cytochrome b. Power saturation experiments performed on the succinate- and dithionite-reduced forms of the enzyme demonstrated that the 4Fe-4S cluster is coupled weakly to both the 2Fe-2S and the 3Fe-4S clusters, Quantitative interpretation of these power saturation experiments has been achieved through redox calculations. They revealed that a spin-spin interaction between the reduced 3Fe-4S cluster and the cytochrome b (oxidized) may also exist. These findings form the first direct EPR evidence for a close proximity (less than or equal to 2 nm) of the high potential 3Fe-4S cluster, situated in the succinate dehydrogenase part of the enzyme, and the low potential, low spin b-heme in the membrane anchor of the enzyme. (Less)
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- Waldeck, A. Reginald ; Stowell, Michael H. B. ; Lee, Hung Kay ; Hung, Shao-Ching ; Matsson, Mikael LU ; Hederstedt, Lars LU ; Ackrell, Brian A.C. and Chan, Sunney I.
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- 1997
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- Journal of Biological Chemistry
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- American Society for Biochemistry and Molecular Biology
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- scopus:0030740917
- ISSN
- 1083-351X
- DOI
- 10.1074/jbc.272.31.19373
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- English
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- 634429c2-bb9c-4cc5-8734-4e68d16088aa
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@article{634429c2-bb9c-4cc5-8734-4e68d16088aa,
abstract = {{Electron paramagnetic resonance (EPR) studies of succinate:ubiquinone oxidoreductase (SQR) from Paracoccus denitrificans have been undertaken in the purified and membrane-bound states, Spectroscopic ''signatures'' accounting for the three iron-sulfur clusters (2Fe-2S, 3Fe-4S, and 4Fe-4S), cytochrome b, flavin, and protein-bound ubisemiquinone radicals have been obtained in air-oxidized, succinate-reduced, and dithionite-reduced preparations at 4-10 K. Spectra obtained at 170 K in the presence of excess succinate showed a signal typical of that of a flavin radical, but superimposed with another signal. The superimposed signal originated from two bound ubisemiquinones, as shown by spectral simulations, Power saturation measurements performed on the air-oxidized enzyme provided evidence for a weak magnetic dipolar interaction operating between the oxidized 3Fe-4S cluster and the oxidized cytochrome b. Power saturation experiments performed on the succinate- and dithionite-reduced forms of the enzyme demonstrated that the 4Fe-4S cluster is coupled weakly to both the 2Fe-2S and the 3Fe-4S clusters, Quantitative interpretation of these power saturation experiments has been achieved through redox calculations. They revealed that a spin-spin interaction between the reduced 3Fe-4S cluster and the cytochrome b (oxidized) may also exist. These findings form the first direct EPR evidence for a close proximity (less than or equal to 2 nm) of the high potential 3Fe-4S cluster, situated in the succinate dehydrogenase part of the enzyme, and the low potential, low spin b-heme in the membrane anchor of the enzyme.}},
author = {{Waldeck, A. Reginald and Stowell, Michael H. B. and Lee, Hung Kay and Hung, Shao-Ching and Matsson, Mikael and Hederstedt, Lars and Ackrell, Brian A.C. and Chan, Sunney I.}},
issn = {{1083-351X}},
language = {{eng}},
publisher = {{American Society for Biochemistry and Molecular Biology}},
series = {{Journal of Biological Chemistry}},
title = {{Electron paramagnetic resonance studies of succinate:ubiquinone oxidoreductase from <em>Paracoccus denitrificans</em> : Evidence for a magnetic interaction between the 3Fe-4S cluster and cytochrome b}},
url = {{http://dx.doi.org/10.1074/jbc.272.31.19373}},
doi = {{10.1074/jbc.272.31.19373}},
year = {{1997}},
}