Polyamines as gating molecules of inward-rectifier K+ channels

Inward-rectifier potassium (K-ir) channels comprise a superfamily of potass ium (K+) channels with unique structural and functional properties. Express ed in virtually all types of cells they are responsible for setting the res ting membrane potential, controlling the excitation threshold and secreting K+ ions. All K-ir channels present an inwardly rectifying current-voltage relation, meaning that at any given driving force the inward flow of K+ ion s exceeds the outward flow for the opposite driving ford. This inward-recti fication is due to a voltage-dependent block of the channel pore by intrace llular polyamines and magnesium. The present molecular-biophysical understa nding of inward-rectification and its physiological consequences is the top ic of this review. In addition to polyamines, K-ir channels an gated by int racellular protons, G-proteins, ATP and phospholipids depending on the resp ective K-ir subfamily as detailed in the following review articles.