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 1H 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 310- and α-helices.Harzianins HC increased the permeability of liposome bilayers and gave rise to voltage-dependent conductance, a property generally observed for longer-sequence peptaibols.