The complete amino acid sequence of subunit d of rat liver mitochondrial H(+)-ATP synthase.

Subunit d of H(+)-ATP synthase from rat liver mitochondria was isolated from the purified enzyme by reverse-phase high performance liquid chromatography. The partial amino acid sequence of the subunit was determined by automated Edman degradation of the peptide fragments. The nucleotide sequence of subunit d of rat liver H(+)-ATP synthase was determined from a recombinant cDNA clone isolated by screening a rat hepatoma cell line H4TG cDNA library with a probe DNA. The sequence was composed of 581 nucleotides including a coding region for the import precursor of subunit d and noncoding regions on the 5'- and 3'- sides. The possible precursor of subunit d and its mature polypeptide deduced from the open reading frame consisted of 161 and 160 amino acid residues with molecular weights of 18,763 and 18,631, respectively. Subunit d is a hydrophilic protein with an isoelectric point of 6.19. The sequence of the rat subunit d is highly homologous with that of subunit d of bovine heart and slightly similar to that of the subunit d of the yeast mitochondria. However, it had no homology with the sequence of any of the subunits of bacterial or chloroplast H(+)-ATP synthase.