| Summary: | 碩士 === 國立臺灣大學 === 微生物學研究所 === 96 === Short cationic antimicrobial peptides are widely present in living organisms for innate defense against invading microorganisms. They are generally amphipathic, small and cationic with at least two positive residues. We demonstrated a synthetic cationic peptide, (R3S1)3, possessing antimicrobial activity, especially against Pseudomonas aeruginosa. Our results showed that the outer membrane proteins of P. aeruginosa, OprI and OprF, interact with the peptide. The antimicrobial activity of (R3S1)3 were repressed by excess amounts of rOprI, rOprF, anti-OprI or anti-OprF. The bacterial membrane became permeable, the chromatin condensed in cytosol and blebs formed on outer membrane of bacteria after (R3S1)3 treatment analyzed by TEM. In addition, the (R3S1)3 translocated across the cytoplasmic membrane, localized in the cytosol of P. aeruginosa and bound to intracellular target, like nucleic acids, analyzed by immunohistochemistry. The (R3S1)3 exerted not only antimicrobial activity but also penetrated eukaryotic cell and nuclear membranes. These action mechanism of antimicrobial peptide (R3S1)3 against P. aeruginosa through the bacterial outer membrane proteins, OprI/OprF, provide important clues for development of new antimicrobial agents.
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