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Kinetics and Thioredoxin Specificity of Thiol Modulation of the Chloroplast H<sup>+</sup>-ATPase
Auteur(s)
Schwarz, Oliver
Schürmann, Peter
Strotmann, Heinrich
Date de parution
1997-03-25
In
The Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology (The), 1997/272/27/16924-16927
Résumé
The kinetics of thiol modulation of the chloroplast H<sup>+</sup>-ATPase (CF<sub>0</sub>CF<sub>1</sub>) <i>in membrana</i> were analyzed by employing thioredoxins that were kept reduced by 0.1 mM dithiothreitol. The kinetics of thiol modulation depend on the extent of the proton gradient. The process is an exponential function of the thioredoxin concentration and reaction time and can be described by an irreversible second order reaction. The results indicate that the formation of the complex between thioredoxin and CF<sub>0</sub>CF<sub>1</sub> is slow compared with the subsequent reduction step. Furthermore we have compared the efficiencies of the Escherichia coli thioredoxin Trx and the two chloroplast thioredoxins Tr-m and Tr-f. The second order rate constants are 0.057 (Tr-f), 0.024 (Trx), and 0.010 s<sup>-1</sup>µM<sup>-1</sup> (Tr-m) suggesting that Tr-f rather than Tr-m is the physiological reductant for the chloroplast ATPase. The often employed artificial reductant dithiothreitol exhibits a second order rate constant in thiol modulation of 1.02•10<sup>-6</sup> s<sup>-1</sup>µM<sup>-1</sup>.
Identifiants
Type de publication
journal article
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