Sequences of Acretocins, Peptaibiotics Containing the Rare 1-Aminocyclopropanecarboxylic Acid, from Acremonium crotocinigenum CBS 217.70

Seven non-ribosomal polypeptide antibiotics, named acretocins (ACRs), were obtained from Acremonium crotocinigenum strain CBS 217.70. The microheterogeneous peptide mixture was isolated from the culture broth by column chromatography on XAD-2 and Sephadex LH-20. Sequences were determined by ESIMSn and amino acid composition by GC/MS. Besides Gly, Leu, and Ala, the peptides contain the nonproteinogenic amino acids Acc (1-aminocyclopropane1-carboxylic acid), Aib (a-aminoisobutyric acid), Iva (isovaline), Pip (pipecolic acid), ss-Ala (ss-alanine), and a C-terminal heterocyclic residue N-peptido-1-isobutyl-2(2,3,4,6,7,8-hexahydro-1-pyrrolo[1,2-a] pyrimidinio) ethylamine (abbreviated X). After vigorous acidic total hydrolysis, release of L-Iva besides D-Iva was established by chiral GC/MS. ACRs show in part sequence identity with neoefrapeptins. Two sequences, ACR5(6), are new: Ac-L-Pip-Aib-L-Pip-D-Iva-D-Iva(Aib)-L-Leu ss-Ala-Gly-Acc-Aib-L-Pip-Aib-L-Ala-L-Leu-L-Iva-X. The taxonomy of fungal producers of acretocins and neoefrapeptins is compared.