Amino-Terminal Blocking Group and Sequence of the Animal Fatty Acid Synthase

We have cloned and sequenced the cDNA encoding the chicken fatty acid synthase. Based on the nucleotide-derived amino acid sequence of the chicken synthase, the N-terminal sequences are highly conserved among animal species, suggesting that translation of the animal synthases initiates with the same ATG codon. Like other fatty acid synthases, the NH2-terminal sequence of the chicken enzyme is blocked. We have isolated and purified the blocked NH2-terminal peptide from a tryptic digest of chicken synthase and have established that the blocking group is an acetyl group. The sequence of the native tryptic peptide confirmed the cDNA-derived amino acid sequence and suggested that all animal synthases begin with this homologous sequence. We developed simple procedures that can be used to isolate and characterize any blocked NH2-terminal peptide.