Effect of phospholipid on the redox potential and enzymic properties of cytochromes b. |
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Authors: | C A Yu L Yu T E King |
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Institution: | Department of Chemistry and Laboratory of Bioenergetics, State University of New York at Albany, 1400 Washington Avenue, Albany, New York 12222 USA |
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Abstract: | The effects of phospholipid on the redox behavior of b cytochromes in succinate-cytochrome c reductase, the cytochrome b-c1 complex, and an isolated cytochrome b preparation were investigated by the oxidative and reductive titrations. Three Em values of cytochrome b were observed in the phospholipid-sufftcient and -depleted succinate-cytochrome c reductase. Their midpoint potentials at pH 7.4 are 75, 75, and ?100 mV for the sufficient and 10, ?30, and ?160 mV for the depleted reductase. The molar distribution of the b cytochromes of these Em values correspond to 30, 30, and 40%, respectively. The Em values of the isolated cytochrome b preparations were not affected by addition of phospholipids. The isolated b preparation contained two components of equal concentration with Em values of ?85 and ?200 mV. No direct correlation between enzymic activity and the amount of high potential b cytochromes present in the systems was demonstrated. Very little difference was observed in redox behavior of b cytochromes between the aged inactive preparations of phospholipid-depleted reductase and that of freshly prepared reconstitutively active enzyme. |
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