Cloning and deduced amino acid sequence of human nicotinamide nucleotide transhydrogenase.

Pyridine nucleotide transhydrogenases (E.C.1.6.1.1) are integral proteins of the inner mitochondrial membrane. These enzymes are part of the energy-transfer system of the respiratory chain and specifically catalyze the transfer of a hydride ion between nicotinamide adenine dinucleotide, NAD(H), and oxidized nicotinamide dinucleotide phosphate, NADP(H). Here we report the sequence of full-length cDNA clone containing the coding sequence for human mitochondrial nicotinamide nucleotide transhydrogenase. The characterized cDNA contains an insert of 4,232 base pairs with a 91% sequence identity to a previously characterized bovine transhydrogenase cDNA. The deduced human polypeptide sequence displays a high degree of sequence similarity, 97%, to the bovine polypeptide and a comparison of the two sequences is presented.