The beta-cell ATP-sensitive potassium channel (KATP channel) comprise the tetrameric ATP-sensitive inward rectifier potassium channel 11 (KCNJ11, Kir6.2) and the tetrameric channel regulator ATP-binding cassette sub-family C member 8 (ABCC8). When the ATP/ADP ratio is high, the KCNJ11 (Kir6.2) subunit binds ATP and the channel closes. Conversely, when the ADP:ATP ratio is high, the ABCC8 (SUR1) subunit binds magnesium-ADP and the channel is open.
The KATP channels in the beta cell are inwardly rectifying (allowing potassium ions to pass out of the cell) and are partially responsible for maintaining the resting potential of the cell, about -70 mV. Closure of the KATP channels causes a depolarization (a reduction in the voltage differential) across the plasma membrane.
The antidiabetic activity of sulfonylurea drugs such as acetohexamide, tolbutamide, glipzide, glibenclamide, and glimepiride is due to their binding ABCC8 (SUR1) subunits and inhibiting potassium efflux.