Artículos de revistas
Coupling of voltage-dependent gating and Ba++ block in the high-conductance, Ca++-activated K+ channel
Fecha
1987Registro en:
Journal of General Physiology, Volumen 90, Issue 3, 2018, Pages 427-449
15407748
00221295
10.1085/jgp.90.3.427
Autor
Miller, Christopher
Latorre, Ramón
Reisin, Ignacio
Institución
Resumen
Voltage-dependent Ca++-activated K+ channels from rat skeletal muscle were reconstituted into planar lipid bilayers, and the kinetics of block of single channels by Ba++ were studied. The Ba++ association rate varies linearly with the probability of the channel being open, while the dissociation rate follows a rectangular hyperbolic relationship with open-state probability. Ba ions can be occluded within the channel by closing the channel with a strongly hyperpolarizing voltage applied during a Ba++-blocked interval. Occluded Ba ions cannot dissociate from the blocking site until after the channel opens. The ability of the closed channel to occlude Ba++ is used as an assay to study the channel’s gating equilibrium in the blocked state. The blocked channel opens and closes in a voltage-dependent process similar to that of the unblocked channel. The presence of a Ba ion destabilizes the closed state of the blocked channel, however, by 1.5 kcal/mol. The results confirm that Ba ions block