title: A family of fluoride-specific ion channels with dual-topology architecture.
abstract: Fluoride ion, ubiquitous in soil, water, and marine environments, is a chronic threat to microorganisms. Many prokaryotes, archea, unicellular eukaryotes, and plants use a recently discovered family of F(-) exporter proteins to lower cytoplasmic F(-) levels to counteract the anion's toxicity. We show here that these 'Fluc' proteins, purified and reconstituted in liposomes and planar phospholipid bilayers, form constitutively open anion channels with extreme selectivity for F(-) over Cl(-). The active channel is a dimer of identical or homologous subunits arranged in antiparallel transmembrane orientation. This dual-topology assembly has not previously been seen in ion channels but is known in multidrug transporters of the SMR family, and is suggestive of an evolutionary antecedent of the inverted repeats found within the subunits of many membrane transport proteins. DOI:http://dx.doi.org/10.7554/eLife.01084.001.
authors.affiliation: Department of Biochemistry , Howard Hughes Medical Institute, Brandeis University , Waltham , United States.
authors.forename: Randy B
authors.initials: RB
authors.lastname: Stockbridge
authors.forename: Janice L
authors.initials: JL
authors.lastname: Robertson
authors.forename: Ludmila
authors.initials: L
authors.lastname: Kolmakova-Partensky
authors.forename: Christopher
authors.initials: C
authors.lastname: Miller
mesh_terms: D000595:Amino Acid Sequence; D019281:Dimerization; D005459:Fluorides / Q000378:metabolism*; D007473:Ion Channels / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
chemical_list: D007473:Ion Channels; D005459:Fluorides
keywords: E. coli; fluoride; ion channel; membrane topology