Structural characterization and cytolytic activity of a potent antimicrobial motif in longicin, a defensin-like peptide in the tick Haemaphysalis longicornis
2010
Rahman, Md,M., Kagoshima Univ. (Japan) | Tsuji, N. | Boldbaatar, D. | Battur, B. | Liao, M. | Umemiya Shirafuji, R. | You, M. | Tanaka, T. | Fujisaki, K.
Longicin, a defensin-like peptide, was recently identified in the hard tick Haemaphysalis longicornis. Longicin and one of its synthetic partial analogs (P4) displayed antimicrobial/fungicidal/parasiticidal activity. In the present study, we compared longicin-derived synthetic analogs in order to characterize the antimicrobial motif (P4) by analyzing some structural features using various bio-informatic tools and/or CD spectroscopy. According to the chemicophysical characteristics, P4 is suggested to be a cationic peptide with hydrophobic and amphipathic character. The predicted secondary structure indicated the existence of a beta-sheet, which was also observed in the modeled tertiary structure. CD spectroscopic results also showed the existence of a beta-sheet and transition to a helical conformation in the presence of membrane-mimicking conditions. These structural observations on P4 suggested that the antimicrobial activity could be due to the beta-sheet as well as the a-helix. In addition, a sequence homology search showed that molecules identified in other ticks and organisms also have the P4 analogous domain at their C-terminal, which indicates P4 as a conserved domain. The peptide P4 also showed low cytolytic activity. Based on the present result and previously reported studies, the peptide P4 could be suggested as a novel antimicrobial domain indicating future therapeutic agent against bacteria.
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