title: Structural characterization and cytolytic activity of a potent antimicrobial motif in longicin, a defensin-like peptide in the tick Haemaphysalis longicornis.
abstract: 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 bioinformatic 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 alpha-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.
authors: Department of Frontier Veterinary Medicine, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan.
authors: Morshedur
authors: M
authors: Rahman
authors: Naotoshi
authors: N
authors: Tsuji
authors: Damdinsuren
authors: D
authors: Boldbaatar
authors: Banzragch
authors: B
authors: Battur
authors: Min
authors: M
authors: Liao
authors: Rika
authors: R
authors: Umemiya-Shirafuji
authors: Myungjo
authors: M
authors: You
authors: Tetsuya
authors: T
authors: Tanaka
authors: Kozo
authors: K
authors: Fujisaki
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects*; D002522:Chlorocebus aethiops; D002942:Circular Dichroism; D023082:Defensins / Q000737:chemistry / Q000494:pharmacology*; D006461:Hemolysis / Q000187:drug effects*; D057927:Hydrophobic and Hydrophilic Interactions; D026863:Ixodidae / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D014709:Vero Cells
chemical_list: D023181:Antimicrobial Cationic Peptides; D023082:Defensins