Cloning and sequencing of the cDNA encoding for a Na+/H+ exchanger from Xenopus laevis oocytes (X1-NHE)

We have cloned and sequenced the cDNA for a Na+/H+ exchanger (NHE) from Xenopus laevis oocytes. This cDNA contains an open reading frame encoding a protein of 782 amino acids with 12 putative transmembrane domains and a long cytoplasmic tail. The protein exhibits a strong homology at the amino acid level to the human NHE-1 as well as to the beta NHE from trout red blood cells: 69% and 58% respectively. Two potential N-linked glycosylation sites at Asn56 and Asn351 were identified. Three potential protein kinase C phosphorylation sites at the cytoplasmic tail were identified at Ser494, Thr726 and Ser747. RT-PCR revealed the expression of the X1-NHE in Xenopus heart, reticulocytes and skeletal muscle.