Molecular cloning, primary structure, and expression of the human growth factor-activatable Na+/H+ antiporter.

Abstract We present the complete sequence of a cDNA encoding the human amiloride-sensitive Na+H+ antiporter. After functional complementation of a mouse fibroblast mutant by gene transfer, we isolated a 0.8 kb genomic probe from a third-cycle mouse transformant. The probe detects gene amplification in Na+H+ antiporter "overexpressers" and a single class of mRNA of ca. 5.6 kb in human, mouse, and hamster cells. With this probe we isolated a 4 kb cDNA from a library constructed from a mouse transformant in which the transfected human gene was amplified. This cDNA includes a noncoding leader of 407 bp, a 2682 bp open reading frame, and a 3′ noncoding sequence cotaining a mouse B1 repeated element. The amino acid sequence predicts a protein of M r = 99,354 with an N-terminal amphipathic domain that contains 10 putative transmembrane-spanning segments and two potential glycosylation sites, followed by a hydrophilic stretch of 395 residues, presumably cytoplasmic. Stable expression of the transfected cDNA in Na+H+ antiporter-deficient cells restored the key functional features of this transporter: H + i -activated Na + influx, amiloride sensitivity, and pH i regulation.