Cloning of the rat heart Na(+)-Ca2+ exchanger and its functional expression in HeLa cells

A functional rat heart Na(+)-Ca2+ exchanger gene has been obtained by splicing and ligating two partially overlapping clones isolated from a rat heart lambda ZAP cDNA library. The deduced primary structure of the protein encoded by the open reading frame corresponds to 971 amino acids, that can be organized into 12 transmembrane helices. The cloned gene was functionally expressed in HeLa cells. Maximal expression was detected 18 h after transfection, after which transport activity rapidly declined. The electrogenic properties of the cloned transporter were demonstrated following reconstitution of the expressed exchanger protein into a tightly sealed phospholipid membrane.