Differences in membrane pore formation by peptaibols.

The efficiencies of membrane pore formation by 14 naturally occurring peptaibols and two structurally modified ampullosporins were compared using an artificial bilayer membrane model. Major differences were found in the dependence on peptide sequences and the constituting amino acids. Alamethicin F-30, chrysospermins C/D, paracelsin and texenomycin A displayed higher activity by several orders of magnitude in comparison with smaller peptaibols containing < 17 amino acids such as ampullosporins, trichofumins.

Crystal structure and conformational analysis of ampullosporin A.

Ampullosporin A is a 15-mer peptaibol type polypeptide that induces pigment formation by the fungus Phoma destructiva, forms voltage-dependent ion channels in membranes and exhibits hypothermic effects in mice. The structure of ampullosporin A has been determined by x-ray crystallography. This is the first three-dimensional (3D) structure of the peptaibol subfamily SF6.

Circular dichroism studies of ampullosporin-A analogues.

Ampullosporin A (AmpA), a 15mer peptalbol containing seven Aib residues is able to induce pigmentation on Phoma destructiva and hypothermia in mice, as well as to exhibit a neuroleptic effect. A circular dichroism study of ampullosporin A and its analogues was carried out in organic solvents with different polarities and detergent micelles to determine the relationship between their conformational flexibility and biological activities. The analogues were obtained by modifying the N- and C-termini of ampullosporin A.

Synthesis and biological evaluation of analogues of the peptaibol ampullosporin A.

A series of analogues of the fungal peptaibol type metabolite ampullosporin A containing modifications in the C and N terminus as well as alpha-aminoisobutyric acid (Aib) substitutions in different positions of the peptide were synthesized by solid phase synthesis using the 9-fluorenylmethyloxycarbonyl strategy. Depending on the sequence position, couplings were performed with 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate/1-hydroxybenzotriazole and tetramethylfluoroformamidinium hexafluorophosphate, respectively. The structures of the target peptides were analyzed by electrospray ionization mass spectrometry and chromatographic methods (high-performance liquid chromatography, thin-layer chromatography).