A protein complex that comprises four pore-forming (Kir6.x) and four regulatory sulphonylurea receptor (SURx) subunits and forms a transmembrane channel through which ions may pass. The opening and closing of the channel is regulated by ATP: binding of ATP to the Kir6.2 subunit inhibits channel activity, whereas binding of Mg2+-complexed ATP or ADP to the SUR1 subunit stimulates channel activity.