To explain the determinants of the cytotoxicity, we investigated the structural parameters of the peptides, their cell-binding properties, cell localization, and dynamics in the membrane, as well as the cell membrane composition. Two promising lead compounds, characterized by the introduction of a positively charged unnatural amino-acid in the hydrophobic face of the helix, selectively kill T67 cancer cells without affecting healthy cells.
Many analogues maintain the same level of non-selective cytotoxicity of TG and three analogues are completely non-toxic. We showed that the cytotoxicity is tuneable by single amino-acids substitutions. In the present work, we studied thirteen TG analogues, adopting a multidisciplinary approach. Trichogin GA IV (TG) is a short peptaibol displaying antimicrobial and cytotoxic activity. Previous studies showed that peptaibols are promising peptide-based drugs because they act against cell membranes rather than a specific target, thus lowering the possibility of the onset of multi-drug resistance, and they possess non-coded α-amino acid residues that confer proteolytic resistance. Peptaibols are peculiar peptides produced by fungi as weapons against other microorganisms.