TY - JOUR TI - The fluoride permeation pathway and anion recognition in Fluc family fluoride channels AU - McIlwain, Benjamin C AU - Gundepudi, Roja AU - Koff, B Ben AU - Stockbridge, Randy B A2 - Maduke, Merritt A2 - Swartz, Kenton J A2 - Maduke, Merritt A2 - Gaudet, Rachelle VL - 10 PY - 2021 DA - 2021/07/12 SP - e69482 C1 - eLife 2021;10:e69482 DO - 10.7554/eLife.69482 UR - https://doi.org/10.7554/eLife.69482 AB - Fluc family fluoride channels protect microbes against ambient environmental fluoride by undermining the cytoplasmic accumulation of this toxic halide. These proteins are structurally idiosyncratic, and thus the permeation pathway and mechanism have no analogy in other known ion channels. Although fluoride-binding sites were identified in previous structural studies, it was not evident how these ions access aqueous solution, and the molecular determinants of anion recognition and selectivity have not been elucidated. Using x-ray crystallography, planar bilayer electrophysiology, and liposome-based assays, we identified additional binding sites along the permeation pathway. We used this information to develop an oriented system for planar lipid bilayer electrophysiology and observed anion block at one of these sites, revealing insights into the mechanism of anion recognition. We propose a permeation mechanism involving alternating occupancy of anion-binding sites that are fully assembled only as the substrate approaches. KW - fluoride KW - ion channel KW - bordetella pertussis JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -