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Ars operon
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<p>In molecular biology, the ars operon is an <a href="/facts/Operon/0m7pJKWn">operon</a> found in several <a href="/facts/Bacteria/wC8xSCsU">bacterial</a> taxon. It is required for the <a href="/facts/Detoxification/SQzAYKQj">detoxification</a> of <a href="/facts/Arsenate/IWco5TAH">arsenate</a>, <a href="/facts/Arsenite/SfFCftGH">arsenite</a>, and <a href="/facts/Antimonite/QXnaNsbh">antimonite</a>. This system transports arsenite and antimonite out of the <a href="/facts/Cell_(biology)/bLM9UQvy">cell</a>. The pump is composed of two polypeptides, the products of the arsA and arsB <a href="/facts/Genes/e1swwPY6">genes</a>. This two-subunit <a href="/facts/Enzyme/DSI1Fh7y">enzyme</a> produces resistance to arsenite and antimonite. Arsenate, however, must first be <a href="/facts/Redox/Pyd5RVcj">reduced</a> to arsenite before it is extruded. A third gene, arsC, expands the <a href="/facts/Enzyme_substrate/6MnaV19h">substrate</a> specificity to allow for arsenate pumping and resistance. ArsC is an approximately 150-residue arsenate <a href="/facts/Reductase/R7ozNahQ">reductase</a> that uses <a href="/facts/Redox/Pyd5RVcj">reduced</a> <a href="/facts/Glutathione/5bSxjusL">glutathione</a> (GSH) to convert arsenate to arsenite with a <a href="/facts/Redox/Pyd5RVcj">redox</a> active <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> <a href="/facts/Residue_(chemistry)/xE6sUTDa">residue</a> in the <a href="/facts/Active_site/u9ua7rGu">active site</a>. ArsC forms an active quaternary <a href="/facts/Protein_complex/GW11Ee34">complex</a> with GSH, arsenate, and <a href="/facts/Glutaredoxin/mqeR7865">glutaredoxin</a> 1 (Grx1). The three <a href="/facts/Ligands/6etB3qeW">ligands</a> must be present simultaneously for <a href="/facts/Redox/Pyd5RVcj">reduction</a> to occur. </p>