The effect of ethanol on the plasma membrane calcium pump is isoform-specific

The effect of ethanol has been studied on four different isoforms of the plasma membrane Ca2+-ATPase expressed in Sf9 cells with the help of the baculovirus system. The PMCA2CI protein was maximally activated by 0.5% ethanol, a concentration 8-10 times lower than that needed to obtain the same effect on the PMCA4 protein or on the pump of erythrocyte membranes, which is a mixture of isoforms 1 and 4. Experiments performed with truncated pumps indicated that the stimulation by ethanol was lost if the C-terminal region between Lys(1065) and Lys(1161), encompassing the calmodulin binding domain, was removed. These observations indicate that the stimulation is the result of a direct interaction of ethanol with the C terminal regulatory domain of the Ca2+ pump.