[Molecular and biophysical aspects of potassium channels].

K+ channels of known sequence fall into two distantly related families, voltage-dependent channels and inwardly rectifying channels. Several types of inwardly rectifying K+ channels, containing two putative transmembrane domains in each subunit, have recently been cloned and can be classified into four groups: 1) IRK family; classical inward rectifying, 2) GIRK family; G-protein-activated, 3) KATP family; ATP-inhibited, and 4) KAB family; ATP-dependent. Recent studies have revealed that atrial and neuronal G-protein-gated inwardly rectifying K+ channels function as heteromultimers of two distinct GIRKs, and that pancreatic beta cell KATP channels are a complex composed of at least two subunits, a member of the ATP-inhibited inwardly rectifying K+ channel family (BIR) and the sulfonylurea receptor.