The K+-ionophores nonactin and valinomycin interact differently with the protein of reconstituted cytochromec oxidase |
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Authors: | Dietmar Steverding Bernhard Kadenbach |
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Institution: | (1) Biochemie, Fachbereich Chemie der Philipps-Universität, Hans-Meerwein-Strasse, D-3550 Marburg, Federal Republic of Germany |
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Abstract: | The K+-ionophores valinomycin and nonactin induce a qualitatively identical change of the visible spectrum of isolated oxidized cytochromec oxidase (red shift), but the amplitude is half with nonactin. Valinomycin, in the presence or absence of a protonophore, stimulates the respiration of the reconstituted enzyme to a higher extent than nonactin and results in a higherK
m
for cytochromec. In contrast, nonactin causes a fivefold rate of proton conductivity across a liposomal membrane, after induction of a K+-diffusion potential. The data indicate that respiratory control by these antibiotics is not only due to degradation of a membrane potential, but rather to specific interaction with and modification of cytochromec oxidase. |
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Keywords: | Cytochromec oxidase valinomycin nonactin respiratory proton conduction protonophore |
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