self-aggregation mechanism and the unique function of cystein residues of the lipid membrane-active peptides

초록

Previously, we identified the active fragment corresponding to C-terminal sheet domain of tenecin 1, an insect defensin from larvae of coleopteran tenbrio molitor and synthesized several peptide analogs of the active fragment. In the present study, we chose this active fragment (TA-1) that contained three Cys residues as a model peptide and investigated the function of Cys residues of the peptide for the mechanism action and the biological activity. Interestingly, TA-1 that had a unique primary structure exhibited a considerable antimicrobial activity in the absence of DTT but did not show antimicrobial activity in the presence of 1.5mM DTT as a reducing agent. Thus, we investigated the interaction between TA-1 and large unilamellar vesicles resembling the lipid composition of S. aureus and C. albicans in the presence and absence of DTT. Surprisingly, TA-1 showed decreased permeabilization activity for lipid membranes depending on the concentration of DTT while the other antibacterial peptides such as magainin, melittin, and brevinine 2E reduced form containing two free Cys residues did not show any dependence of the permeabilization activity on the concentration of DTT. Furthermore, we investigated the interaction of TA-1 with the vesicles with different surface charges in the presence or absence of 1.5mM DTT. As surface charge of the vesicles decreased, the relative effect of DTT on the membrane permeabilization activity of the peptide decreased, which indicated that DTT must prevent the disulfide bridge formation of the peptide on the surface of the vesicles.