ANTIBIOTIC PEPTIDES FROM TRICHODERMA-HARZIANUM - HARZIANINS HC, PROLINE-RICH 14-RESIDUE PEPTAIBOLS

An original group of antibiotic-antifungal peptides of the peptaibol class, the harzianins HC, was isolated from T. harzianum strains selected for their antagonistic properties against phytopathogenic fungi. Eleven peptides were isolated by reversed-phase HPLC from the original complex mixtures, and sequenced. The sequences resulted both from positive-ion FAB-MS and H-1 NMR data. Harzianins HC are 14-residue peptaibols containing three Aib-L-Pro motives at positions 4-5, 8-9 and 12-13. ROESY data and amide temperature coefficient values agreed with a helical structure stabilised by hydrogen bonds of the 4-->1 type and looking to differ from 3(10)- and alpha-helices. Harzianins HC increased the permeability of liposome bilayers and gave rise to voltage-dependent conductance, a property generally observed for longer-sequence peptaibols.