Title: Molecular cloning and nucleotide sequence of cDNA encoding the entire precursor of rat liver medium chain acyl coenzyme A dehydrogenase.
Abstract: cDNA encoding the precursor of rat liver medium chain acyl-CoA dehydrogenase (EC 1.3.99.3) was cloned and sequenced.The longest cDNA insert isolated was 1866 bases in length.This cDNA encodes the entire protein of 421-amino acids including a 25-amino acid leader peptide and a 396-amino acid mature polypeptide.The identity of the medium chain acyl-CoA dehydrogenase clone was confirmed by matching the amino acid sequence predicted from the cDNA to the NHz-terminal and nine internal tryptic peptide sequences derived from pure rat liver medium chain acyl-CoA dehydrogenase, The calculated molecular masses of the precursor medium chain acyl-CoA dehydrogenase, the mature medium chain acyl-CoA dehydrogenase, and the leader peptide are 46,600, 43,700, and 2,900 daltons, respectively.The leader peptide contains five basic amino acids and only one acidic amino acid; thus, it is positively charged, overall.Cysteine residues are unevenly distributed in the mature portion of the protein; five of six are found within the NH2-terminal half of the polypeptide.Comparison of medium chain acyl-CoA dehydrogenase sequence to other flavoproteins and enzymes which act on coenzyme A ester substrates did not lead to unambiguous identification of a possible FAD-binding site nor a coenzyme A-binding domain.The sequencing of other homologous acyl-CoA dehydrogenases will be informative in this regard.Medium chain acyl-CoA dehydrogenase (EC 1.3.99.3) is one of the five known acyl-CoA dehydrogenases.It acts on a wide spectiam of straight chain acyl-coenzyme A esters of medium chain length (1) and plays a crucial role in fatty acid oxidation.Other enzymes in this group are short chain acyl-CoA, long chain acyl-CoA, isovaleryl-CoA, and 2-methyl-branched chain ~~~