Crystal structures of a double-barrelled fluoride ion channel
- Autores: Randy B. Stockbridge, Ludmila Kolmakova Partensky, Tania Shane, Akiko Koide, Shohei Koide, Christopher Miller, Simon Newstead
- Localización: Nature: International weekly journal of science, ISSN 0028-0836, Vol. 525, Nº 7570, 2015, págs. 548-551
- Idioma: inglés
- Enlaces
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Resumen
To contend with hazards posed by environmental fluoride, microorganisms export this anion through F--specific ion channels of the Fluc family1,2,3,4. 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 assembly5,6. 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 Å. 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.
