The contribution of RCK domains to human BK channel allosteric activation

摘要: Large conductance voltage- and Ca2+-activated K+ (BK) channels are potent regulators of cellular processes including neuronal firing, synaptic transmission, cochlear hair cell tuning, insulin release, smooth muscle tone. Their unique activation pathway relies on structurally distinct regulatory domains one transmembrane voltage-sensing domain (VSD) two intracellular high affinity Ca2+-sensing sites per subunit (located in the RCK1 RCK2 domains). Four pairs form a apparatus known as “gating ring.” The allosteric interplay between apparati is fundamental mechanism BK channel function. Using voltage-clamp fluorometry UV photolysis caged Ca2+, we optically resolved VSD prompted by Ca2+ binding to gating ring. sudden increase concentration ([Ca2+]i) induced hyperpolarizing shift voltage dependence both opening activation, reported fluorophore labeling position 202, located upper side S4 segment. neutralization sensor abolished effect [Ca2+]i rearrangements. On other hand, mutation residues involved sensing did not prevent release VSD, revealing functionally interaction VSD. A statistical-mechanical model quantifies complex thermodynamics association sites, opening.