pH-dependent, voltage-insensitive, background potassium channel protein. Rectification direction results from potassium ion concentration on either side of the membrane. Acts as an outward rectifier when external potassium concentration is low. When external potassium concentration is high, current is inward. Homodimer. Heterodimer with KCNK1. Very strong expression in heart, also detected in kidney, brain, skin, testis, lung, skeletal muscle, small intestine and stomach. Not detected in liver, thymus or spleen. Inactivated by barium. Belongs to the two pore domain potassium channel (TC 1.A.1.8) family.