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. Strongest expression in heart. Moderate expression in lung and brain. Low levels in liver, kidney and skeletal muscle. Inhibited by extracellular acidification, zinc, bupivacaine and phenytoin. Activated by protein kinase A. Belongs to the two pore domain potassium channel (TC 1.A.1.8) family.