The 2TM domain family of K channels are also known as the inward-rectifier channel family. This includes strong (Kir2.x) that constitutively active, G-protein-activated (Kir3.x) and ATP-sensitive (Kir6.x, which combine with sulphonylurea receptors (SUR1-3)). pore-forming α subunits form tetramers, heteromeric may be formed within subfamilies (e.g. Kir3.2 Kir3.3).
