MOLECULAR-CLONING OF CDNA-ENCODING MITOCHONDRIAL VERY-LONG-CHAIN ACYL-COA DEHYDROGENASE FROM BOVINE HEART

To clone the cDNA encoding an isoenzyme of mitochondrial very-long-cha in acyl-CoA dehydrogenase (VLCAD) from bovine heart lambda gt11 and la mbda gt10 cDNA libraries. METHODS: The clone was isolated with immunos creening technique and validated by (1) the microsequences of the N-te rminus and three internal proteolytic fragments from the purified enzy me; (2) identification of the acyl-CoA dehydrogenase (AD) signature se quence; and (3) high homology of the deduced peptide sequences, as exp ected, with those of rat liver mitochondrial VLCAD. RESULTS: The cDNA (2203 bp) corresponds to a similar to 2.4-kb mRNA band from the same t issue source revealed by a Northern blotting. The deduced peptide sequ ence of 655 amino acids (70 537 Da) is composed of a 40-amino acid mit ochondrial leader peptide moiety (4 346 Da) and a 615-amino acid pepti de as a mature protein (66 191 Da). A comparison of the peptide sequen ces in the AD family shows the major diversity in their signal sequenc es, suggesting a structural basis for their different mitochondrial lo cations. The catalytic sites are all highly conserved among VLCAD. Ser -251 analogous to and Cys-215 diversified to other family members. A p seudo-consensus sequence of leucine zipper was found in the C-terminal region from Leu-568 to Leu-589, implying a mechanism whereby the dime r of this protein is formed by zipping these leucine residues from the alpha-helixes of 2 monomers. CONCLUSION: The isolated cDNA clone enco des an isoenzyme of mitochondrial VLCAD in bovine heart.