BK channels

Large conductance, voltage, and Ca2+-activated K+ channels are known as BK or MaxiK channels to denote the large single channel conductance of 100-300 pS (Figure 17.1). BK channel currents were rst discovered in the early 1980s when the newly invented patch clamp techniques were used to record various cell types, and their large single channel currents stood out from patch clamp recordings with intracellular solutions containing Ca2+ (1, 2). A decade later, the gene that encodes the pore-forming a subunit of BK channels, slo1 or KCNMA1, was rst identied in Drosophila (3, 4), and then in mouse (5) and human (6, 7). BK channels activate in response to membrane depolarization and elevation of intracellular Ca2+ concentrations: the open probability of single BK channels increases with voltage and intracellular Ca2+ concentrations (Figure 17.1), while the macroscopic conductance (G) of many BK channels increases with voltage and the conductance-voltage (G-V) relation shifts toward more negative voltages with increasing intracellular Ca2+ concentrations (Figure 17.2). e dependence of BK channel activation on both voltage and Ca2+ makes the channel function versatile in two unique aspects. First, BK channel function is not dened by any single voltage or intracellular Ca2+ concentrations; the G-V relation of BK channels varies depending on the intracellular Ca2+ concentrations at which it is measured, while the dose-response curve of channel activation on intracellular Ca2+ concentrations also changes with voltage (8, 9). Second, the channel function varies with voltages changing from -200 to +300 mV and intracellular Ca2+ concentrations variations from 0 to 10 mM (9) that cover all possible physiological and pathological conditions.

Duke Scholars

Author Huanghe Yang Biochemistry