We have isolated and characterized a full length cDNA clone encoding the precursor of the human heart mitochondrial phosphate carrier protein. The entire clone is 1330 bp in length with 5'- and 3'-untranslated regions of 48 and 184 bp, respectively. The open reading frame encodes the mature protein consisting of 312 amino acids, preceded by a presequence of 49 amino acids. The amino acid sequence of the mature human phosphate carrier is 93.6, 94.2 and 33.6% identical to that of the phosphate carrier from beef, rat and yeast, respectively. Like other mitochondrial transport proteins, the human phosphate carrier has a tripartite structure. Each of the three repeats contains two hydrophobic regions which presumably span the membrane in the form of alpha-helices.