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Electron paramagnetic resonance studies of succinate:ubiquinone oxidoreductase from Paracoccus denitrificans : Evidence for a magnetic interaction between the 3Fe-4S cluster and cytochrome b

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. (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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Journal of Biological Chemistry
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ASBMB
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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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yes
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634429c2-bb9c-4cc5-8734-4e68d16088aa
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2017-07-18 09:57:47
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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    = {ASBMB},
  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},
  year         = {1997},
}