Highly conserved N-methyltransferases as an integral part of peptide synthetases

The methyltransferase portion of the N-methyl-peptide-synthetase gene, synthesizing enniatin from Fusarium sambucinum, was amplified with the polymerase chain reaction (PCR) using primers derived from the highly conserved sequences of the flanking peptide synthetase domain. The deduced amino acid sequence of the product shares high similarity to the 430 amino acid methyltransferase portion of enniatin synthetase of Fusarium scirpi and the corresponding portions of another fungal peptide synthetase catalyzing the biosynthesis of the N-methylated cyclopeptide cyclosporin. As the methyltransferase portions show only local similarity to motifs apparently conserved within methyltransferases, the segments of peptide synthetases involved in the biosynthesis of bioactive peptides represent a new class of S-adenosyl-L-methionine dependent methyltransferases.