Plasma Membrane Calcium-Transporting ATPase
The existence of a plasma membrane calcium-transporting ATPase (PMCA) that actively pumps Ca2+ ions out of the cell was first demonstrated in erythrocyte (red blood cell) membranes by Schatzmann (1966). Because of its generally low abundance and difficult biochemical properties, it took over a decade until the PMCA was first isolated in purified form. Crucial for the successful purification was the discovery that the PMCA binds with high affinity, and in a Ca2+-dependent manner, to the Ca2+ sensor protein calmodulin (Niggli et al. 1979). Subsequent work showed that at least one type of plasma membrane Ca2+ ATPase is found in all eukaryotic cells including those from fungi, animals, and plants (Axelsen and Palmgren 1998; Thever and Saier 2009). It is now well established that active Ca2+ expulsion by the PMCAs is an essential component of eukaryotic cellular Ca2+handling. Although PMCAs were...
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