Effect of calmodulin,Ca2+ and Mg2+ on the (Ca2+ + Mg2+)-ATPase of erythrocyte membranes |
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Authors: | Reinhard Klinger Reinhard Wetzker Inga Fleischer Horst Frunder |
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Institution: | Institute of Physiological Chemistry, University of Jena, DDR-6900 Jena, GDR |
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Abstract: | Calmodulin-depleted isotonic erythrocyte ghosts contain 200 ng residual calmodulin/mg protein which is not removed by extensive washings at pCa2+ > 7. Specific activity and Ca2+-affinity of the (Ca2+ + Mg2+)ATPase increase at increasing calmodulin, with K0.5 Ca of 0.38 μM at calmodulin concentrations corresponding to that in erythrocytes. High Ca2+ concentrations inhibit the enzyme. Specific activity and Ca2+-affinity of the enzyme decrease at increasing Mg2+ concentrations. The Ca2+ ? Mg2+ antagonism is likewise observed at inhibitory Ca2+ concentrations. |
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Keywords: | reprint requests to RK |
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