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Structure of the E148A mutant of CLC-ec1 deltaNC construct in 100mM fluoride and 20mM Bromide
Structural highlights
FunctionCLCA_ECOLI Proton-coupled chloride transporter. Functions as antiport system and exchanges two chloride ions for 1 proton. Probably acts as an electrical shunt for an outwardly-directed proton pump that is linked to amino acid decarboxylation, as part of the extreme acid resistance (XAR) response.[1] [2] [3] [4] [5] Publication Abstract from PubMedCl-/H+ antiporters of the CLC superfamily transport anions across biological membranes in varied physiological contexts. These proteins are weakly selective among anions commonly studied, including Cl-, Br-, I-, NO3- and SCN-, but they seem to be very selective against F-. The recent discovery of a new CLC clade of F-/H+ antiporters, which are highly selective for F- over Cl-, led us to investigate the mechanism of Cl--over-F- selectivity by a CLC Cl-/H+ antiporter, CLC-ec1. By subjecting purified CLC-ec1 to anion transport measurements, electrophysiological recording, equilibrium ligand-binding studies and X-ray crystallography, we show that F- binds in the Cl- transport pathway with affinity similar to Cl- but stalls the transport cycle. Examination of various mutant antiporters implies a 'lock-down' mechanism of F- inhibition, in which F-, by virtue of its unique hydrogen-bonding chemistry, greatly retards a proton-linked conformational change essential for the transport cycle of CLC-ec1. Fluoride-dependent interruption of the transport cycle of a CLC Cl/H antiporter.,Lim HH, Stockbridge RB, Miller C Nat Chem Biol. 2013 Sep 15. doi: 10.1038/nchembio.1336. PMID:24036509[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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