The sodium/calcium exchangers are a family of integral membrane proteins. This domain covers the integral membrane regions of these proteins. Sodium/calcium exchangers regulate intracellular Ca2+ concentrations in many cells; cardiac myocytes, epithelial cells, neurons retinal rod photoreceptors and smooth muscle cells [<cite idref="PUB00005133"/>]. Ca2+ is moved into or out of the cytosol depending on Na+ concentration [<cite idref="PUB00005133"/>]. In humans and rats there are 3 isoforms; NCX1 NCX2 and NCX3 [<cite idref="PUB00002973"/>].