The influence of calcium pump coupling on the Arrhenius behavior of sarcoplasmic reticulum Ca2+-ATPase |
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| Authors: | Martin D. King Peter J. Quinn Felix M. Munkonge Thomas D. Madden |
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| Affiliation: | (1) Department of Biochemistry, King's College London, Campden Hill, W8 7AH London, UK;(2) Present address: Abteilung Spektroskopie, Max Planck Institut fur Biophysikalische Chemie, Göttingen, Germany;(3) Present address: Department of Physiology and Biochemistry, University of Southampton, SO9 3TU Southampton, UK;(4) Present address: Department of Biochemistry, The University of British Columbia, V6T 1W5 Vancouver, B.C., Canada |
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| Abstract: | Experiments were performed in which two batches of sarcoplasmic reticulum were isolated from rabbit hind leg muscle, one in the presence of dithiothreitol, the other in the absence of reducing agent. A comparative study was made of some of the properties of the two preparations, in particular, the Arrhenius behavior of the Ca2+-ATPase. The Ca2+-ATPase isolated in the absence of dithiothreitol is thermally unstable with the result that a triphasic Arrhenius plot was obtained. This triphasic behavior is largely the consequence of an uncoupling of the hydrolytic machinery from the calcium pump. In contrast, the sarcoplasmic reticulum preparation obtained in the presence of dithiothreitol is thermally stable and yields a linear Arrhenius plot. The difference in the Arrhenius behavior shown by the two preparations was abolished when the measurements of Ca2+-ATPase activity were made in the presence of the calcium ionophore, A23187. |
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| Keywords: | Calcium-ATPase Arrhenius behavior sarcoplasmic reticulum ATPase |
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