Arsenical pump ATPase, ArsA
InterPro Protein Domain record
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<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>Active extrusion is a common mechanism for the detoxification of heavy metals, drugs and antibiotics in bacteria, protozoa and mammals. This is particularly important for arsenic extrusion because of its prevalence in the environment and its potential to cause health and environmental problems. In prokaryotes, arsenic detoxification is accomplished by chromosomal and plasmid-borne operon-encoded efflux systems. Bacterial ArsA ATPase is the catalytic component of an oxyanion pump that is responsible for resistance to arsenite (As(III)) and antimonite (Sb(III)). <taxon tax_id="6239">Caenorhabditis elegans</taxon> has a homologue (asna-1) [<cite idref="PUB00043521"/>]. </p><p>ArsA from <taxon tax_id="562">Escherichia coli</taxon> is the catalytic subunit of the ArsAB extrusion pump, providing resistance to arsenite and antimonite. This pump consists of a soluble ATPase (ArsA) and a membrane channel (ArsB). Maintenance of a low intracellular concentration of oxyanion produces resistance to the toxic agents. A third protein, ArsC, expands the substrate specificity to allow for arsenate resistance. ArsC reduces arsenate to arsenite, which is subsequently pumped out of the cell [<cite idref="PUB00007982"/>].</p><p>ArsA contains two nucleotide-binding sites (NBSs) and a binding site for arsenic or antimony. Binding of metalloids to the pump stimulates the ATPase activity [<cite idref="PUB00024783"/>].</p>
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Arsenical pump ATPase, ArsA
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