KCa3.1 is part of the Ca2+ activated K+ channels family that share the characteristic of being activated by intracellular Ca2+. The channel has an intermediate conductance, is voltage insensitive and is activated by Ca2+ in the submicromolar range. The channel has a similar topology to that of KV channels, that is six transmembrane domains and intracellular N- and C-termini. nKCa3.1 is widely expressed in epithelial, endothelial and cells of hematopoietic origin. In erythrocytes (red blood cells) it has been identified as the molecular correlate of the so-called Gardos channel.