Calpain I Activates Ca2+ Transport by the Human Erythrocyte Plasma Membrane Calcium Pump
Many extracellular signals, including hormones, exert their effects on cells by elevating free Ca2+ concentration. For this reason, it is important for a resting cell to maintain a submicromolar concentration of free Ca2+ in the cytosol. In red cells, this function is largely provided by the plasma membrane-bound Ca2+- translocating ATPase. Both Ca2+ translocating and ATP-hydrolytic activities of this enzyme are stimulated by calmodulin (CaM) via reversible binding (see Al-Jobore et al., 1981). We recently reported an irreversible means of activating the ATP-hydrolytic activity of the enzyme, involving the cytosolic Ca2+ -dependent protease (calpain I) (Wang et al., 1988a; 1988b). However, it is not yet established whether the calcium translocating activity of the enzyme is also activated by calpain I. In this study, we further examine the effect of calpain I on the liposome-reconstituted calcium pump.
KeywordsRelative Molecular Mass Calcium Pump Dependent Protease Submicromolar Concentration Pump Molecule
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- Al-Jobore, A., Mauldin, D., Minocherhomjee, A.M., and Roufogalis, B.D., 1981, in: “Erythrocyte Membranes 3: Recent Clinical and Experimental Advances”, W.C. Kruckeberg, J.W. Eaton, and G.J. Brewer, eds., pp 757–773, Alan R. Liss, New York.Google Scholar