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Electron paramagnet...
Electron paramagnetic resonance studies of succinate:ubiquinone oxidoreductase from Paracoccus denitrificans : Evidence for a magnetic interaction between the 3Fe-4S cluster and cytochrome b
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- Waldeck, A. Reginald (författare)
- California Institute of Technology
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- Stowell, Michael H. B. (författare)
- California Institute of Technology
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- Lee, Hung Kay (författare)
- California Institute of Technology
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- Hung, Shao-Ching (författare)
- California Institute of Technology
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Matsson, Mikael (författare)
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- Hederstedt, Lars (författare)
- Lund University,Lunds universitet,Molekylär cellbiologi,Biologiska institutionen,Naturvetenskapliga fakulteten,Molecular Cell Biology,Department of Biology,Faculty of Science
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- Ackrell, Brian A.C. (författare)
- University of California, San Francisco
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- Chan, Sunney I. (författare)
- California Institute of Technology
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(creator_code:org_t)
- Elsevier BV, 1997
- 1997
- Engelska.
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Ingår i: Journal of Biological Chemistry. - : Elsevier BV. - 1083-351X .- 0021-9258.
- Relaterad länk:
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http://dx.doi.org/10... (free)
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http://www.jbc.org/c...
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https://lup.lub.lu.s...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- 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.
Ämnesord
- NATURVETENSKAP -- Biologi -- Mikrobiologi (hsv//swe)
- NATURAL SCIENCES -- Biological Sciences -- Microbiology (hsv//eng)
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