Abstract
The recently detected Rieske iron-sulfur center in the membrane of the thermoacidophilic archaeon Sulfolobus acidocaldarius (Anemüller et al., 1993, FEBS Lett. 318, 61-64) was further characterized by EPR spectroscopy, coupled to redox-potentiometry and functional studies. The reduction potential is pH-dependent above pH 6, revealing the influence of two ionization equilibria in the oxidized form, with pKaox-values of 6.2 and 8.5. Above pH 9, the slope of the curve is--120 mV/pH-unit. A partially purified fraction exerted a ubiquinol-cytochrome c oxidoreductase activity. To our knowledge, for the first time, in a membrane bound Rieske iron-sulfur protein, unequivocal evidence for a two proton dependent redox equilibrium is presented.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Animals
-
Ascorbic Acid / pharmacology
-
Cell Membrane / metabolism
-
Cytochrome c Group / metabolism
-
Electron Transport Complex III*
-
Horses
-
Hydrogen-Ion Concentration
-
Iron-Sulfur Proteins / isolation & purification
-
Iron-Sulfur Proteins / metabolism*
-
Kinetics
-
Membrane Proteins / isolation & purification
-
Membrane Proteins / metabolism
-
Myocardium / metabolism
-
Oxidation-Reduction
-
Sulfolobus acidocaldarius / metabolism*
-
Ubiquinone / analogs & derivatives
-
Ubiquinone / pharmacology
Substances
-
Cytochrome c Group
-
Iron-Sulfur Proteins
-
Membrane Proteins
-
Rieske iron-sulfur protein
-
Ubiquinone
-
2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone
-
Electron Transport Complex III
-
Ascorbic Acid