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. Can be blocked by external barium. Associates with GIRK1 or GIRK2 to form a G-protein-activated heteromultimer pore-forming unit. The resulting inward current is much larger. Most abundant in heart tissue where it is found predominantly in atria. Also found in brain, kidney, liver, spleen, lung and thymus. Belongs to the inward rectifier-type potassium channel (TC 1.A.2.1) family. KCNJ5 subfamily.