The ATP-sensitive potassium (KATP) channel couples glucose metabolism to insulin secretion in pancreatic b-cells. It comprises regulatory sulfonyl-urea receptor 1 and pore-forming subunits. Binding and⁄or hydro-lysis of Mg-nucleotides at the nucleotide-binding domains of sulfonylurea receptor 1 stimulates channel opening and leads to membrane hyperpolari-zation and inhibition of insulin secretion.