title: Structure of the antimicrobial peptide tachystatin A.
abstract: The solution structure of antimicrobial peptide tachystatin A from the Japanese horseshoe crab (Tachypleus tridentatus) was determined by two-dimensional nuclear magnetic resonance measurements and distance-restrained simulated annealing calculations. The correct pairs of disulfide bonds were also confirmed in this study. The obtained structure has a cysteine-stabilized triple-stranded beta-sheet as a dominant secondary structure and shows an amphiphilic folding observed in many membrane-interactive peptides. Interestingly, tachystatin A shares structural similarities with the calcium channel antagonist omega-agatoxin IVA isolated from spider toxin and mammalian defensins, and we predicted that omega-agatoxin IVA also have the antifungal activity. These structural comparisons and functional correspondences suggest that tachystatin A and omega-agatoxin IVA may exert the antimicrobial activity in a manner similar to defensins, and we have confirmed such activity using fungal culture assays. Furthermore, tachystatin A is a chitin-binding peptide, and omega-agatoxin IVA also showed chitin-binding activities in this study. Tachystatin A and omega-agatoxin IVA showed no structural homology with well known chitin-binding motifs, suggesting that their structures belong to a novel family of chitin-binding peptides. Comparison of their structures with those of cellulose-binding proteins indicated that Phe(9) of tachystatin A might be an essential residue for binding to chitin.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Fujitani
authors.forename: Shun-ichiro
authors.initials: S
authors.lastname: Kawabata
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Osaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kumaki
authors.forename: Makoto
authors.initials: M
authors.lastname: Demura
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Nitta
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kawano
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry* / Q000378:metabolism; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D001665:Binding Sites; D005075:Biological Evolution; D002686:Chitin; D006737:Horseshoe Crabs / Q000276:immunology*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D020867:omega-Agatoxin IVA / Q000737:chemistry
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D020867:omega-Agatoxin IVA; C461649:tachystatin A; D002686:Chitin