The function of KCNJ8 (potassium inwardly rectifying channel subfamily J member 8, ENSG00000121361) is as follows. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it (PubMed:20558321, PubMed:21836131, PubMed:24700710, PubMed:28842488). 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 (PubMed:20558321, PubMed:21836131, PubMed:24700710, PubMed:28842488). The inward rectification is mainly due to the blockage of outward current by internal magnesium. This channel is activated by internal ATP and can be blocked by external barium (PubMed:20558321, PubMed:21836131, PubMed:24700710, PubMed:28842488). Can form a sulfonylurea-sensitive but ATP-insensitive potassium channel with ABCC9 (By similarity). {ECO:0000250|UniProtKB:P97794, ECO:0000269|PubMed:20558321, ECO:0000269|PubMed:21836131, ECO:0000269|PubMed:24700710, ECO:0000269|PubMed:28842488}.