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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
3
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pubmed:dateCreated |
1992-10-26
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pubmed:abstractText |
The redox potential of the Rieske [2Fe-2S] cluster of the bc1 complex from bovine heart mitochondria was determined by cyclic voltammetry of a water-soluble fragment of the iron/sulfur protein. At the nitric-acid-treated bare glassy-carbon electrode, the fragment gave an immediate and stable quasireversible response. The midpoint potential at pH 7.2, 25 degrees C and I of 0.01 M was Em = +312 +/- 3 mV. This value corresponds within 20 mV to results of an EPR-monitored dye-mediated redox titration. With increasing ionic strength, the midpoint potential decreased linearly with square root of I up to I = 2.5 M. From the cathodic-to-anodic peak separation, the heterogeneous rate constant, k degrees, was calculated to be approximately 2 x 10(-3) cm/s at low ionic strength; the rate constant increased with increasing ionic strength. From the temperature dependence of the midpoint potential, the standard reaction entropy was calculated as delta S degrees = -155 J.K-1.mol-1. The pH dependence of the midpoint potential was followed over pH 5.5-10. Above pH 7, redox-state-dependent pK changes were observed. The slope of the curve, -120 mV/pH above pH9, indicated two deprotonations of the oxidized protein. The pKa values of the oxidized protein, obtained by curve fitting, were 7.6 and 9.2, respectively. A group with a pKa,ox of approximately 7.5 could also be observed in the optical spectrum of the oxidized protein. Redox-dependent pK values of the iron/sulfur protein are considered to be essential for semiquinone oxidation at the Qo center of the bc1 complex.
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Electron Transport Complex III,
http://linkedlifedata.com/resource/pubmed/chemical/Iron-Sulfur Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Peptide Fragments,
http://linkedlifedata.com/resource/pubmed/chemical/Rieske iron-sulfur protein
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pubmed:status |
MEDLINE
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pubmed:month |
Sep
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pubmed:issn |
0014-2956
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
15
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pubmed:volume |
208
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
685-91
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pubmed:dateRevised |
2007-7-23
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pubmed:meshHeading |
pubmed-meshheading:1327764-Animals,
pubmed-meshheading:1327764-Cattle,
pubmed-meshheading:1327764-Electrochemistry,
pubmed-meshheading:1327764-Electron Spin Resonance Spectroscopy,
pubmed-meshheading:1327764-Electron Transport Complex III,
pubmed-meshheading:1327764-Hydrogen-Ion Concentration,
pubmed-meshheading:1327764-Iron-Sulfur Proteins,
pubmed-meshheading:1327764-Mitochondria, Heart,
pubmed-meshheading:1327764-Osmolar Concentration,
pubmed-meshheading:1327764-Peptide Fragments,
pubmed-meshheading:1327764-Solubility,
pubmed-meshheading:1327764-Thermodynamics
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pubmed:year |
1992
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pubmed:articleTitle |
Determination of the redox properties of the Rieske [2Fe-2S] cluster of bovine heart bc1 complex by direct electrochemistry of a water-soluble fragment.
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pubmed:affiliation |
Universitätsklinikum Frankfurt, Zentrum für Biologische Chemie, Therapeutische Biochemie, Federal Republic of Germany.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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