NCX_Mj - Sodium-Calcium Exchanger - Uncharacterized membrane protein MJ0091

Family:
Calcium-Cation Antiporter family (CaCA)

Subgrops:
The CaCA superfamily is composed of five families: K⁺-independent Na⁺/Ca²⁺ exchangers (NCXs), cation/Ca²⁺ exchangers (CCXs), YbrG transporters and cation exchangers (CAXs). Phylogenetic and alignment studies indicate that one of the mammalian NCKXs, NCKX6, and its related proteins form a unique group, designated cation/Ca²⁺ exchangers (CCXs)

Topology:
Proteins of the CaCA family are found ubiquitously, having been identified in animals, plants, yeast, archaea and divergent bacteria. They exhibit widely divergent sequences, and several have been shown to have arisen by a tandem intragenic duplication event. The most conserved portions of this repeat element, α1 and α2, are found in putative transmembrane regions 2-3 and transmembrane regions 7-8. Members of this family contain nine transmembrane regions in mammals.

Function:
All of the characterized animal proteins catalyze Ca²⁺:Na⁺ exchange although some also transport K⁺. The NCX plasma membrane proteins exchange 3 Na⁺ for 1 Ca²⁺. Mammalian Na²⁺/Ca²⁺ exchangers exist as three isoforms NCX1-3 which are about 70% identical to each other.