[Antibacterial activity and mechanisms of a new peptide derived from cell-penetrating peptide].

ABSTRACT

OBJECTIVE: We studied the antibacterial activities and mechanism of a new peptide P7, according to the structure-activity relationships of cell-penetrating peptide and antimicrobial peptide. METHODS: The antimicrobial activities and cytotoxicity of P7 were examined using the microdilution and hemolysis analysis. The effects of P7 on the outer and plasma membrane permeability, membrane integrity and morphology of E. coli cells were analyzed by the membrane fluorescent probe, flow cytometry and scanning electron microscopy. Localization of the P7 onto the E. coli cells was determined by using a confocal laser-scanning microscopy. The DNA binding activity of P7 was evaluated by electrophoretic mobility shift assay. RESULTS: P7 possessed stronger antimicrobial activity than ppTG20. The inhibitory concentration was in the range from 4 to 32 micromol/L where P7 shown low hemolysis. P7 could increase the outer and plasma membrane permeability, induce the cell membrane integrity loss and cells structure damage. P7 penetrated the cell membrane, accumulated inside the cytoplasm and interacted with DNA. CONCLUSION: P7 exerted its antibacterial activity by increasing cell membrane permeability, penetrated the cell membrane and binding to DNA.