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Membrane Biology "j Springer-Verlag New York Inc. 1989 Calpain I Activates Ca2+ Transport by the Reconstituted Erythrocyte Ca2+ Pump

By Kevin Ko, W Wang, Basil Do Roufogalis and Antonio Villalobo


Summary: Calpain I purified from human erythrocyte cytosol activates both the A TP hydrolytic activity and the A TP-dependent Ca2+ transport function of the Ca2+-translocating ATPase solubilized and purified from the plasma membrane of human erythrocytes and reconstituted into phosphatidylcholine vesicles. Following partial proteolysis of the enzyme by calpain I, both the initial rates of calcium ion uptake and A TP hydrolysis were increased to near maximal levels similar to those obtained upon addition of calmodulin. The proteolytic activation resulted in the loss of further stimulation of the rates of Ca2+ translocation or A TP hydrolysis by calmodulin as well as an increase of the affinity of the enzyme for calcium ion. However, the mechanistic Ca2+/ATP stoichiometric ratio was not affected by the proteolytic treatment of the reconstituted Ca2+-translocating ATPase. The proteolytic activation of the A TP hydrolytic activity of th

Year: 2014
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