KCNJ9 belongs to the inward rectifier-type potassium channel family and is controlled by G proteins. It associates with another G-protein-activated potassium channel to form a heteromultimeric pore-forming complex. 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.