Subunit of ATP-sensitive potassium channels (KATP). Can form cardiac and smooth muscle-type KATP channels with KCNJ11. KCNJ11 forms the channel pore while ABCC9 is required for activation and regulation. Interacts with KCNJ11. Isoforms SUR2A and SUR2B are found in cerebellum, eye, atrium, ventricle, urinary bladder and skeletal muscle. Isoform SUR2B is also found in forebrain, liver, lung, pancreas, kidney, spleen, stomach, small intestine, colon, uterus, ovary and fat tissue. Isoform SUR2C is expressed exclusively in the heart. Belongs to the ABC transporter superfamily. ABCC family. Conjugate transporter (TC 3.A.1.208) subfamily.