The Applications And Mechanism Of Melittin-related Peptides In Antibacterial And Gene Transfection

Abstract:Melittin is a typical antibacterial peptide from bee venom. Melittin has broad biological activity, such as antibacterial, antiviral, antitumor, as well as improving cationic polymer mediated gene transfection. However, high cytotoxicity of melittin hampers its applications. In previous study, we found that two melittin-related peptides, RV-23from Rana draytonii and AR-23from Rana tagoi, exhibited higher antibacterial activity and higher potent for improving gene transfection efficiency, but lower cytotoxicity than melittin.Objectives:One aim of this project is to study the interactions of antibacterial peptides with membrane of mammalian cell and bacteria, their antibacterial activity, so as to study the selective antibacterial mechanism of RV-23and its biocompatibility. Another purpose of this project is to study the effect of positive charge at c-terminus of AR-23on its function and to evaluate its possibility as an enhancer for cationic polymers mediated gene transfection.Methods:Melittin, RV-23, AR-23, AR-20(truncated peptide of AR-23) and AR-26(with the same positively charged residues as melittin) were synthesized. The second structural of peptides was examined by circular dichroism (CD) spectroscopy. The antibacterial activity to Escherichia coli and Staphylococcus aureus was detected by microdilution method. Peptide-induced depolarization of cell membrane, the membrane-lytic activity of the peptides and their potency in enhancing cellular uptake of calcein were evaluated. The effect of the peptides on PEI mediated transfection was determined by using GFP and luciferase as reporter gene. Biocompatibility of peptides was investigated by detecting their effect on blood components, such as, platelets activation, conformation change of albumin and blood coagulation.Results:Both RV-23and AR-23had typical α-helical structure. RV-23could selectively bind with bacterial cells, induced membrane depolarization and disruption which lead to death. RV-23did not interact with the membrane of human cells. Therefore, RV-23had low hemolytic activity, cytotoxicity. AR-23did not selective mechanism. The endosome disruptive activity of AR-23was higher than that of melittin, while its hemolytic activity and cytotoxicity was lower than melittin. AR-23showed higher potency in improving PEI mediated transfection than melittin.Conclusions:RV-23may be considered as a potential antibacterial drug with low toxicity due to its selective killing effect on bacterial cells. While, AR-23with less positively charged residues than melittin may be considered as a potential enhancer for improving cationic polymers due to its high endosome disrupting activity and low cytotoxicity. There are26figures and52references in the paper.