title: Trichogin GA IV: a versatile template for the synthesis of novel peptaibiotics.
abstract: Trichogin GA IV, isolated from the fungus Trichoderma longibrachiatum, is the prototype of lipopeptaibols, the sub-class of short-length peptaibiotics exhibiting membrane-modifying properties. This peptaibol is predominantly folded in a mixed 3(10)-/α- helical conformation with a clear, albeit modest, amphiphilic character, which is likely to be responsible for its capability to perturb bacterial membranes and to induce cell death. In previous papers, we reported on the interesting biological properties of trichogin GA IV, namely its good activity against Gram positive bacteria, in particular methicillin-resistant S. aureus strains, its stability towards proteolytic degradation, and its low hemolytic activity. Aiming at broadening the antimicrobial activity spectrum by increasing the peptide helical amphiphilicity, in this work we synthesized, by solution and solid-phase methodologies, purified and fully characterized a set of trichogin GA IV analogs in which the four Gly residues at positions 2, 5, 6, 9, lying in the poorly hydrophilic face of the helical structure, are substituted by one (position 2, 5, 6 or 9), two (positions 5 and 6), three (positions 2, 5, and 9), and four (positions 2, 5, 6, and 9) Lys residues. The conformational preferences of the Lys-containing analogs were assessed by FT-IR absorption, CD and 2D-NMR techniques in aqueous, organic, and membrane-mimetic environments. Interestingly, it turns out that the presence of charged residues induces a transition of the helical conformation adopted by the peptaibols (from 3(10)- to α-helix) as a function of pH in a reversible process. The role played in the analogs by the markedly increased amphiphilicity was further tested by fluorescence leakage experiments in model membranes, protease resistance, antibacterial and antifungal activities, cytotoxicity, and hemolysis. Taken together, our biological results provide evidence that some of the least substituted among these analogs are good candidates for the development of new membrane-active antimicrobial agents.
authors.affiliation: ICB, Padova Unit, CNR, Department of Chemistry, University of Padova, 35131, Padova, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: De Zotti
authors.forename: Barbara
authors.initials: B
authors.lastname: Biondi
authors.forename: Cristina
authors.initials: C
authors.lastname: Peggion
authors.forename: Fernando
authors.initials: F
authors.lastname: Formaggio
authors.forename: Yoonkyung
authors.initials: Y
authors.lastname: Park
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Hahm
authors.forename: Claudio
authors.initials: C
authors.lastname: Toniolo
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects; D005658:Fungi / Q000187:drug effects; D006801:Humans; D055666:Lipopeptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D055666:Lipopeptides; C116419:trichogin GA IV