title: State-dependent FRET reports calcium- and voltage-dependent gating-ring motions in BK channels.
abstract: Large-conductance voltage- and calcium-dependent potassium channels (BK, "Big K+") are important controllers of cell excitability. In the BK channel, a large C-terminal intracellular region containing a "gating-ring" structure has been proposed to transduce Ca(2+) binding into channel opening. Using patch-clamp fluorometry, we have investigated the calcium and voltage dependence of conformational changes of the gating-ring region of BK channels, while simultaneously monitoring channel conductance. Fluorescence resonance energy transfer (FRET) between fluorescent protein inserts indicates that Ca(2+) binding produces structural changes of the gating ring that are much larger than those predicted by current X-ray crystal structures of isolated gating rings.
authors.affiliation: Research Division, University Hospital of Nuestra Señora de Candelaria, 38010 Tenerife, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Miranda
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Contreras
authors.forename: Andrew J R
authors.initials: AJ
authors.lastname: Plested
authors.forename: Fred J
authors.initials: FJ
authors.lastname: Sigworth
authors.forename: Miguel
authors.initials: M
authors.lastname: Holmgren
authors.forename: Teresa
authors.initials: T
authors.lastname: Giraldez
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018360:Crystallography, X-Ray; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D014981:Xenopus
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D002118:Calcium