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A CLC-type F−/H+ antiporter in ion-swapped conformations
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June 25 2018
Source: Nat Struct Mol Biol. 25(7):601-606
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Alternative Title:Nat Struct Mol Biol
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Description:Fluoride/proton antiporters of the CLC| family combat F| toxicity in bacteria by exporting this halide from the cytoplasm. These transporters belong to the widespread CLC superfamily but display transport properties different from those of the well-studied Cl|/H| antiporters. Here, we report a structural and functional investigation of these F|-transport proteins. Crystal structures of a CLC| homolog from Enterococcus casseliflavus are captured in two conformations with simultaneous accessibility of F| and H| ions via separate pathways on opposite sides of the membrane. Manipulation of a key glutamate residue critical for H| and F| transport reverses the anion selectivity of transport; replacement of the glutamate with glutamine or alanine completely inhibits F| and H| transport while allowing for rapid uncoupled flux of Cl|. The structural and functional results lead to a 'windmill' model of CLC antiport wherein F| and H| simultaneously move through separate ion-specific pathways that switch sidedness during the transport cycle.
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Pubmed ID:29941917
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Pubmed Central ID:PMC6044475
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