ATP-sensitive potassium channel regulatory subunit (Sulfonylurea receptor, SUR) (SUR)

The ATP-sensitive potassium channel regulatory subunit (Sulfonylurea receptor, SUR) is a key component of the ATP-sensitive potassium channel (KATP) complex. KATP channels are hetero-octameric complexes composed of four pore-forming Kir6.x subunits and four regulatory SUR subunits, which belong to the ATP-binding cassette (ABC) transporter superfamily[2][4]. SUR subunits do not form the ion-conducting pore themselves; instead, they regulate the activity of the channel in response to intracellular ATP and ADP, thereby linking cellular metabolic status to electrical excitability[1][3]. Different SUR isoforms (SUR1, SUR2A, SUR2B) combine with Kir6.1 or Kir6.2 to form channels with distinct tissue distributions and pharmacological properties[4]. SUR1 is predominantly found in pancreatic β-cells, where its inhibition by sulfonylurea drugs stimulates insulin secretion[2][5]. SUR2 isoforms are prevalent in cardiac, skeletal, and smooth muscle, where they participate in the regulation of vascular tone and cardiac protection during ischemia[3][4]. Mutations in SUR subunits can lead to metabolic disorders, emphasizing their importance as both physiological regulators and therapeutic targets[2][4]. The SUR subunit is unique among ABC proteins in that it regulates, rather than transports, an ion channel[2].

Other names

Sulfonylurea receptorSUR1SUR2SUR2ASUR2BABC transporterATP-binding cassette transporterKATP channel regulatory subunit

Sulfonylureas bind to SUR subunits, promoting KATP channel closure and increasing insulin secretion; KATP channel openers bind to SUR and promote channel opening, leading to relaxation of vascular smooth muscle and reduced insulin secretion[1][5]. The regulatory subunit (SUR) undergoes Mg-nucleotide-dependent conformational changes that modulate channel activity in response to ADP[2][5].