[Molecular mechanism of the K+ATP channel in pancreatic beta-cells]

The ATP-sensitive K+ (K+ATP) channel plays a key role in secretion of insulin in response to glucose-stimulation in pancreatic beta-cells. Inhibition of the channel does not require hydrolysis of ATP and results from a direct binding of ATP4- to the channel. MgADP relieves the channel inhibition by ATP by decreasing affinity of the channel to ATP. We suggest two-sites model regarding channel modulations by these nucleotides; one is the ATP-inhibition site which is bound by ATP4-, and the other the modulation site, which is bound by MgADP and thereby decreases the sensitivity of the channel to ATP. Sulphonylureas-binding sites may be different from these nucleotide-binding sites described above.