Primary structures of rat and bovine liver mitochondrial aldehyde dehydrogenases deduced from cDNA sequences

The cDNA coding for rat liver mitochondrial aldehyde dehydrogenase was cloned and sequenced. It contained an open reading frame of 1557 bp. Of the deduced 519 amino acid residues, 19 were proposed to correspond to the signal peptide necessary to allow the protein to enter the mitochondria [Farrés, J., Guan, K.-L. and Weiner, H. (1987) Biochem. Biophys. Res. Commun. 150, 1083 - 1087]. The sequence of the 500 amino acid residues comprising the mature subunit was 96% identical to that of the corresponding human liver mitochondrial enzyme. The longest cDNA isolated coding for the bovine liver enzyme contained sequence information corresponding to residues 72 - 500 of the rat or human enzyme. The deduced protein sequence of these residues was 94% identical to those of the human enzyme. Over 60% of the bases in the coding region of the rat cDNA were G and C. These residues were clustered non-randomly and two potentially stable stem-loop structures could be calculated as existing in the mRNA. One would be found in the region coding for amino acid residues 64 - 79; a similar secondary structure could be responsible for the existing truncated cDNAs from the bovine-cDNA libraries. Comparisons with the amino acid sequences of other aldehyde dehydrogenases support the suggestion that the NAD-binding domain may be located in the middle portion of the mature enzyme.