Na+/Ca2+ exchanger: structure, function, regulation

The Na/Ca exchanger of the plasma membrane is a reversible transporter that couples the translocation of 3 sodium against 1 calcium. Its activity is particularly important to excitable tissues. Three homologous exchanger genen products (NCX1-2-3) are differently expressed in heart, brain and kidney. Hydropathy analysis has indicated 11 hydrophobic segments with highly conserved regions that have been suggested to play a role in ion transport. The mRNA levels of the exchanger are controlled by tissue-specific promoters. In some cell type (e.g. neurons) they are modulated by calcium. The regulatory mechanisms of autoinhibition and activation by calcium and ATP are linked to domains in the large central cytosolic loop of the protein