<p>ATPases (or ATP synthases) are membrane-bound enzyme complexes/ion transporters that combine ATP synthesis and/or hydrolysis with the transport of protons across a membrane. ATPases can harness the energy from a proton gradient, using the flux of ions across the membrane via the ATPase proton channel to drive the synthesis of ATP. Some ATPases work in reverse, using the energy from the hydrolysis of ATP to create a proton gradient. There are different types of ATPases, which can differ in function (ATP synthesis and/or hydrolysis), structure (e.g., F-, V- and A-ATPases, which contain rotary motors) and in the type of ions they transport [<cite idref="PUB00020603"/>, <cite idref="PUB00020604"/>]. The different types include:</p><p> <ul><li>F-ATPases (F1F0-ATPases), which are found in mitochondria, chloroplasts and bacterial plasma membranes where they are the prime producers of ATP, using the proton gradient generated by oxidative phosphorylation (mitochondria) or photosynthesis (chloroplasts).</li><li>V-ATPases (V1V0-ATPases), which are primarily found in eukaryotic vacuoles and catalyse ATP hydrolysis to transport solutes and lower pH in organelles.</li><li>A-ATPases (A1A0-ATPases), which are found in Archaea and function like F-ATPases (though with respect to their structure and some inhibitor responses, A-ATPases are more closely related to the V-ATPases).</li><li>P-ATPases (E1E2-ATPases), which are found in bacteria and in eukaryotic plasma membranes and organelles, and function to transport a variety of different ions across membranes.</li><li>E-ATPases, which are cell-surface enzymes that hydrolyse a range of NTPs, including extracellular ATP.</li> </ul> </p><p>P-ATPases (sometime known as E1-E2 ATPases) (<db_xref db="EC" dbkey="3.6.3.-"/>) are found in bacteria and in a number of eukaryotic plasma membranes and organelles [<cite idref="PUB00009616"/>]. P-ATPases function to transport a variety of different compounds, including ions and phospholipids, across a membrane using ATP hydrolysis for energy. There are many different classes of P-ATPases, each of which transports a specific type of ion: H⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ag⁺ and Ag²⁺, Zn²⁺, Co²⁺, Pb²⁺, Ni²⁺, Cd²⁺, Cu⁺ and Cu²⁺. P-ATPases can be composed of one or two polypeptides, and can usually assume two main conformations called E1 and E2.</p><p>This entry represents P-type ATPases that specialise in cation and copper transport; those transporting copper (<db_xref db="EC" dbkey="3.6.3.4"/>) have been classified as belonging to the IB subfamily [<cite idref="PUB00020657"/>, <cite idref="PUB00020658"/>, <cite idref="PUB00009611"/>]. These proteins are involved in a variety of processes in both prokaryotes and eukaryotes. Some of these P-ATPases import copper into cells, such as in Arabidopsis sp., which require copper to create functional hormone receptors for ethylene signalling. Other P-ATPases are involved in copper export out of cells, such as occurs with the efflux of hepatic copper into the bile in eukaryotes. In bacteria, some of these P-ATPases play a role in osmotic adaptation. Certain copper ATPases have been implicated in both Wilson and Menkes diseases [<cite idref="PUB00020659"/>].</p><p>More information about this protein can be found at Protein of the Month: ATP Synthases [<cite idref="PUB00020719"/>].</p> ATPase, P type, cation/copper-transporter