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.x subunit inhibits channel activity, whereas binding of Mg2+-complexed ATP or ADP to the SURx subunit stimulates channel activity. [ http://www.ncbi.nlm.nih.gov/pubmed/16308567 http://www.ncbi.nlm.nih.gov/pubmed/16956886 ]