Calcium ATPase

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Calcium ATPase

Ca²⁺ ATPase is a form of P-ATPase that transfers calcium after a muscle has contracted. The calcium ATPase are:

• Plasma membrane Ca²⁺ ATPase (PMCA)
• Sarcoplasmic reticulum Ca²⁺ ATPase (SERCA)

Plasma membrane Ca²⁺ ATPase (PMCA)

Main article: Plasma membrane calcium ATPase

Rendered image of the Ca²⁺ pump

The plasma membrane Ca²⁺ ATPase (PMCA) is a transport protein in the plasma membrane of cells that serves to remove calcium (Ca²⁺) from the cell. It is vital for regulating the amount of Ca²⁺ within cells. In fact, the PMCA is involved in removing Ca²⁺ from all eukaryotic cells. There is a very large transmembrane electrochemical gradient of Ca²⁺ driving the entry of the ion into cells, yet it is very important for cells to maintain low concentrations of Ca²⁺ for proper cell signalling; thus it is necessary for the cell to employ ion pumps to remove the Ca²⁺. The PMCA and the sodium calcium exchanger (NCX) are together the main regulators of intracellular Ca²⁺ concentrations. Since it transports Ca²⁺ into the extracellular space, the PMCA is also an important regulator of the calcium concentration in the extracellular space.

The PMCA belongs to a family of P-type primary ion transport ATPases that form an aspartyl phosphate intermediate.

The PMCA is expressed in a variety of tissues, including the brain.

Sarcoplasmic reticulum Ca²⁺ ATPase (SERCA)

Main article: SERCA

SERCA resides in the sarcoplasmic reticulum (SR) within muscle cells. It is a Ca²⁺ ATPase that transfers Ca²⁺ from the cytosol of the cell to the lumen of the SR at the expense of ATP hydrolysis during muscle relaxation.

See also

• Active transport#Counter-transport

External links

• Calcium ATPase at the US National Library of Medicine Medical Subject Headings (MeSH)
• EC 3.6.3.8
• Overview at utoronto.ca
• Cation transporting ATPase family in Pfam
• UMich Orientation of Proteins in Membranes families/superfamily-22 - Calculated orientations of calcium ATPase in membrane