Functional regulation of BK potassium channels by γ1 auxiliary subunits

Many K+ channels are oligomeric complexes with intrinsic structural symmetry arising from the homo-tetrameric core of their pore-forming subunits. Allosteric regulation of tetramerically symmetric proteins, whether by intrinsic sensing domains or associated auxiliary subunits, often mirrors the fourfold structural symmetry. Here, through patch-clamp recordings of channel population ensembles and also single channels, we examine regulation of the Ca2+- and voltage-activated large conductance Ca2+-activated K+ (BK) channel by associated gamma 1-subunits. Through expression of differing ratios of gamma 1: alpha-subunits, the results reveal an all-or-none functional regulation of BK channels by gamma-subunits: channels either exhibit a full gating shift or no shift at all. Furthermore, the gamma 1-induced shift exhibits a state-dependent labile behavior that recapitulates the fully shifted or unshifted behavior. The gamma 1-induced shift contrasts markedly to the incremental shifts in BK gating produced by 1-4 beta-subunits and adds a new layer of complexity to the mechanisms by which BK channel functional diversity is generated.