Calcium pump

The plasma membrane Ca²⁺ ATPase and the sodium-calcium exchanger are together the main regulators of cytoplasmic Ca²⁺ concentrations.

Biological role

Ca²⁺ has many important roles as an intracellular messenger. The release of a large amount of free Ca²⁺ can trigger a fertilized egg to develop, skeletal muscle cells to contract, secretion by secretory cells and interactions with Ca²⁺ -responsive proteins like calmodulin. To maintain low concentrations of free Ca²⁺ in the cytosol, cells use membrane pumps like calcium ATPase found in the membranes of sarcoplasmic reticulum of skeletal muscle. These pumps are needed to provide the steep electrochemical gradient that allows Ca²⁺ to rush into the cytosol when a stimulus signal opens the Ca²⁺ channels in the membrane. The pumps are also necessary to actively pump the Ca²⁺ back out of the cytoplasm and return the cell to its pre-signal state.