Ca²⁺-Translocating ATPase of the Plant Plasma Membrane

For Ca(2+) to function as a second messenger in signal transduction, it is essential that plant cells maintain low cytoplasmic Ca(2+) levels relative to internal organelles and the apoplast. At the plasma membrane, Ca(2+) is actively transported out of the cytoplasm and current evidence supports the involvement of a primary Ca(2+)-translocating ATPase in mediating this energy-dependent process. This review examines the preliminary biochemical characterization of this transport enzyme.