Membrane Perturbation Action Mode and Structure-Activity Relationships of Protonectin, a Novel Antimicrobial Peptide from the Venom of the Neotropical Social Wasp Agelaia pallipes pallipes

With the extensive use of antibiotics, multidrug-resistant bacteria emerge frequently. New antimicrobial agents with novel modes of action are urgently needed. It is now widely accepted that antimicrobial peptides (AMPs) could be promising alternatives to conventional antibiotics. In this study, we aimed to study the antimicrobial activity and mechanism of action of protonectin, a cationic peptide from the venom of the neotropical social wasp Agelaia pallipes pallipes. We demonstrated that protonectin exhibits potent antimicrobial activity against a spectrum of bacteria, including multidrug-resistant strains. To further understand this mechanism, the structural features of protonectin and its analogs were studied by circular dichroism (CD). The CD spectra demonstrated that protonectin and its natural analog polybia-CP formed a typical alpha-helical conformation in the membrane-mimicking environment, while its proline-substituted analog had much lower or even no alpha-helix conformation. Molecular dynamics simulations indicated that the alpha-helical conformation in the membrane is required for the exhibition of antibacterial activity. In conclusion, protonectin exhibits potent antimicrobial activity by disruption of the integrity of the bacterial membrane, and its alpha-helical confirmation in the membrane is essential for this action.