Antifungal membranolytic activity of the tyrocidines against filamentous plant fungi.

The tyrocidines and analogues are cyclic decapeptides produced by Brevibacillus parabrevis with a conserved sequence of cyclo(D-Phe-Pro-X-x-Asn-Gln-X-Val-X-Leu) with Trp/Phe in the aromatic dipeptide unit, Lys/Orn as their cationic residue and Tyr (tyrocidines), Trp (tryptocidines) or Phe (phenicidines) in position 7. Previous studies indicated they have a broad antifungal spectrum with the peptides containing a Tyr residue in position 7 being more active than those with a Phe or Trp residue in this position. Detailed analysis of antifungal inhibition parameters revealed that Phe-D-Phe in the aromatic dipeptide unit lead to more consistent activity against the three filamentous fungi in this study.