[Show abstract][Hide abstract] ABSTRACT: With the extensive use of antibiotics, multidrug resistant bacteria emerge frequently. New antimicrobial agents with novel mode 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 its mechanism-of-action of protonectin, a cationic peptide from the venom of neotropical social wasp Agelaia pallipes pallipes. We demonstrated that protonectin exhibited potent antimicrobial activity against a spectrum of bacteria, including multi-drug resistant stains. To further understand the mechanism, the structure 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 typical α-helical conformation in the membrane mimicking environment, while its praline-substituted analog had much lower, even no α-helix conformation. MD simulations indicated that the α-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 α-helical confirmation in the membrane is essential for this action.
[Show abstract][Hide abstract] ABSTRACT: As the frequent emergence of the resistant bacteria, the development of new agents with a new action mode attracts a great deal of interest. It is now widely accepted that antimicrobial peptides (AMPs) are promising alternatives to conventional antibiotics. In this study, antimicrobial peptide polybia-MPI and its analogs were synthesized and their antibacterial activity was studied. Our results revealed that polybia-MPI has potent antibacterial activity against both Gram-positive and Gram-negative bacteria. Its ability to make PI permeate into bacteria and lead to the leakage of calcein from model membrane LUVs, suggests a killing mechanism involving membrane perturbation. SEM and TEM microscopy experiments verified that the morphology of bacteria was changed greatly under the treatment of polybia-MPI. Compared with the conventional chemotherapy, polybia-MPI targets the cell membrane rather than entering into the cell to exert its antibacterial activity. Furthermore, molecular dynamics (MD) simulations were employed to investigate the mechanism of membrane perturbation. The results indicated that the α-helical conformation in the membrane is required for the exhibition of antibacterial activity and the membrane disturbance by polybia-MPI is a cooperative process. In conclusion, with the increasing resistance to conventional antibiotics, there is no doubt that polybia-MPI could offer a new strategy to defend the resistant bacteria.
[Show abstract][Hide abstract] ABSTRACT: Antimicrobial peptide polybia-CP was purified from the venom of the social wasp Polybia paulista. It has an amphipathic sequence ILGTILGLLKSL-NH(2) and possesses potent antimicrobial activity against both Gram-positive and Gram-negative bacteria. In this study we synthesized polybia-CP, studied its cytotoxity on tumor cells and proposed its possible mechanism. Our results revealed that polybia-CP exerts its cytotoxic efficacy by disrupting the integrity of cell membrane. Furthermore, molecular dynamics (MD) simulations were employed to investigate the mechanism of membrane perturbation. Both the MD simulations and the experimental data indicated that polybia-CP takes a standard α-helix conformation in the membrane. These findings together with the other experimental results support a speculation of mechanism similar to the "carpet" model.
[Show abstract][Hide abstract] ABSTRACT: Transportan 10 (TP10) is an amphipathic cell-penetrating peptide with high translocation ability. In order to obtain more details of structure-activity relationship of TP10, we evaluated the effects of structure and charge on its translocation ability. Our results demonstrated that disrupting the helical structure or Arg substitution could remarkably decrease the cellular uptake of TP10. However, increasing the number of positive charge was an effective strategy to enhance translocation ability of TP10. Furthermore, the molecular dynamics simulation supported the results derived from experiments, suggesting that higher membrane disturbance leads to higher cellular uptake of peptides. In addition, our study also demonstrated TP10 and its analogs preferentially entered cancer cells rather than normal cells. The uptake selectivity toward cancer cells makes TP10 and its analogs as potent CPPs for drug delivery.