This potassium channel is controlled by G proteins. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. Their voltage dependence is regulated by the concentration of extracellular potassium; as external potassium is raised, the voltage range of the channel opening shifts to more positive voltages. The inward rectification is mainly due to the blockage of outward current by internal magnesium. This receptor plays a crucial role in regulating the heartbeat.
Using this approach, we identified s385 as an in vitro phosphorylation site. Mutation of this residue to alanine resulted in a reduced sensitivity of kir3.1* currents to h89 and forskolin, confirming an in vivo role for this novel site of the kir3.1 channel subunit in its regulation by pka.
The muscarinic k(+) channel (i (k,ach)) is a heterotetramer composed of girk1 (kir3.1) andgirk4(kir3.4) subunits of a g protein-coupled inwardly rectifying channel, and plays an important role in mediating electrical responses to the vagal stimulation in the heart.