Na+/Ca2+ exchanger (NCX) are membrane transporters that play an essential role in maintaining the homeostasis of cytosolic Ca2+ for cell signalling. Ca2+ is moved into or out of the cytosol depending on Na+ concentration NCX is a symmetrical structure containing ten transmembrane helices, divided in two halves with a similar structure but opposite orientation. Based on its symmetry, NCX is able to catalyse bidirectional ion-exchange reactions. Four ion-binding sites cluster at the centre of the protein: one specific for Ca2+ and three that likely bind Na+. Two passageways allow for Na+ and Ca2+ access to the central ion-binding sites from the extracellular side.

This superfamily entry represents the two peripheral helices.

PFAM:PF01699,INTERPRO:IPR004837,DOI:10.1126/science.1215759,DOI:10.1038/nsmb.3230