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Publication Abstract from PubMed

To contend with hazards posed by environmental fluoride, microorganisms export this anion through F(-)-specific ion channels of the Fluc family. Since the recent discovery of Fluc channels, numerous idiosyncratic features of these proteins have been unearthed, including strong selectivity for F(-) over Cl(-) and dual-topology dimeric assembly. To understand the chemical basis for F(-) permeation and how the antiparallel subunits convene to form a F(-)-selective pore, here we solve the crystal structures of two bacterial Fluc homologues in complex with three different monobody inhibitors, with and without F(-) present, to a maximum resolution of 2.1 A. The structures reveal a surprising 'double-barrelled' channel architecture in which two F(-) ion pathways span the membrane, and the dual-topology arrangement includes a centrally coordinated cation, most likely Na(+). F(-) selectivity is proposed to arise from the very narrow pores and an unusual anion coordination that exploits the quadrupolar edges of conserved phenylalanine rings.

Crystal structures of a double-barrelled fluoride ion channel.,Stockbridge RB, Kolmakova-Partensky L, Shane T, Koide A, Koide S, Miller C, Newstead S Nature. 2015 Sep 24;525(7570):548-51. doi: 10.1038/nature14981. Epub 2015 Sep 7. PMID:26344196^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.