alamethicin and paracelsin

Fifteen strains of Trichoderma belonging to 12 different species for potential use in biological control were examined for their ability to produce polypeptide antiobitics (peptaibols). Gas chromatography was used to detect the hydrolysis products of peptaibols after esterification with n-propanol and derivatisation with heptafluorobutyric anhydride. In particular, amino acids (alpha-aminoisobutyric acid, and isovalin) and amino alcohols (phenylalaninol, leucinol, and valinol) were used as markers for the detection of different peptaibols. alpha-Aminoisobutyric acid, an amino acid characterising all peptaibols, was detected in all cultures examined, indicating that the production of peptaibols is a common feature of the various Trichoderma species. Different amino acid/amino alcohol combinations suggested specific peptaibol production. On this basis, the peptaibol paracelsin was confirmed by HPTLC in 11 out of 15 Trichoderma strains cultures. Valinol was not found in any culture extract, indicating the lack of trichotoxins production. Culture extracts of the 6 tested Trichoderma strains were extremely toxic to Artemia salina larvae; for 5 of them this toxicity could be attributed to paracelsin (calculated LD50 = 2.2 microM).

Topics: Alamethicin; Amino Acid Sequence; Amino Acids; Amino Alcohols; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Artemia; Biological Assay; Chromatography, Gas; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Culture Media; Dose-Response Relationship, Drug; Geotrichum; Hydrolysis; Lethal Dose 50; Molecular Sequence Data; Peptides; Trichoderma

The effect of different representatives of the group of peptaibiotics, alpha-amino-isobutyric acid rich secondary metabolites of filamentous fungi, on Culex pipiens larvae was studied. Light and transmission electron microscopy techniques were used to localize the intracellular damage and to determine the target organells for the mode of action of peptaibols in mosquito larvae. Though different in insecticidal activity, all tested compounds induced the same type of tissue damage, which was characterized by heavy challenge of mitochondria followed by partial swelling, crystaeolysis and destruction of mitochondrial walls. It is concluded that the mode of action of peptaibols in mosquito larvae is mediated through the damage of mitochondria. The structure-mosquitocidal effect of these compounds, their potential mode of action and role in the natural fungal entomopathogenic process are briefly discussed.

Topics: Alamethicin; Amino Acid Sequence; Aminoisobutyric Acids; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Culicidae; Fungi; Insecticides; Intercellular Signaling Peptides and Proteins; Larva; Mitochondria; Molecular Sequence Data; Organic Chemicals; Peptaibols; Peptides; Peptides, Cyclic

Paracelsin, a hemolytic and membrane active polypeptide antibiotic of the peptaibol class which is excreted by the mold Trichoderma reesei, was obtained by a simplified and rapid isolation procedure utilizing hydrophobic adsorber resins. Investigation by 13C nuclear magnetic resonance spectroscopy and circular dichroism revealed considerable helical portions in solution, and the very recently accomplished sequence determination of paracelsin allows the discussion of the results with regard to the closely related analogues, alamethicin and suzukacillin. A selective cleavage of the peptide was achieved by careful treatment with various acids, and a buffer of pH 8.25 and of high ionic strength made possible the quantitative determination of the C-terminal phenylalaninol released by means of ion-exchange chromatography. The significance of the production of paracelsin and related mycotoxins of the peptaibol class, exhibiting various kinds of biological activity, is discussed with respect to the extensive effort being made towards biotechnological applications of species, strains and cellulolytically highly active mutants of the fungus Trichoderma.

Topics: Alamethicin; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Chromatography; Chromatography, High Pressure Liquid; Circular Dichroism; Erythrocytes; Hemolysis; Humans; Magnetic Resonance Spectroscopy; Molecular Conformation; Peptides; Phenylalanine; Trichoderma