Candidacidal mechanism of a Leu/Lys-rich α-helical amphipathic model antimicrobial peptide and its diastereomer composed of D,L-amino acids

✍ Scribed by Peng Wang; Yong Hai Nan; Song Yub Shin

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 854 KB
• Volume: 16
• Category: Article
• ISSN: 1075-2617
• DOI: 10.1002/psc.1268

✦ Synopsis

Abstract

We investigated the mechanism of candidacidal action of a Lys/Leu‐rich α‐helical model antimicrobial peptide (K~9~L~8~W) and its diastereomeric peptide (D~9~‐K~9~L~8~W) composed of D,L‐amino acids. K~9~L~8~W killed completely Candida albicans within 30 min, but D~9~‐K~9~L~8~W killed only 72% of C. albicans even after 100 min. Tryptophan fluorescence spectroscopy indicated that the fungal cell selectivity of D~9~‐K~9~L~8~W is closely correlated with a selective interaction with the negatively charged PC/PE/PI/ergosterol (5:2.5:2.5:1, w/w/w/w) phospholipids, which mimic the outer leaflet of the plasma membrane of C. albicans. K~9~L~8~W was able to induce almost 100% calcein leakage from PC/PE/PI/ergosterol (5:2.5:2.5:1, w/w/w/w) liposomes at a peptide:lipid molar ratio of 1:16, whereas D~9~‐K~9~L~8~W caused only 25% dye leakage even at a peptide:lipid molar ratio of 1:2. Confocal laser‐scanning microscopy revealed that FITC‐labeled D~9~‐K~9~L~8~W penetrated the cell wall and cell membrane and accumulated inside the cells, whereas FITC‐labeled K~9~L~8~W did not penetrate but associated with the membranes. Collectively, our results demonstrated that the candidacidal activity of K~9~L~8~ W and D~9~‐K~9~L~8~W may be due to the transmembrane pore/channel formation or perturbation of the fungal cytoplasmic membranes and the inhibition of intracellular functions, respectively. Finally, D~9~‐K~9~L~8~W with potent anti‐Candida activity but no hemolytic activity may be potentially a useful lead compound for the development of novel antifungal agents. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.