title: The solution structure of horseshoe crab antimicrobial peptide tachystatin B with an inhibitory cystine-knot motif.
abstract: Tachystatin B is an antimicrobial and a chitin-binding peptide isolated from the Japanese horseshoe crab (Tachypleus tridentatus) consisting of two isopeptides called tachystatin B1 and B2. We have determined their solution structures using NMR experiments and distance geometry calculations. The 20 best converged structures of tachystatin B1 and B2 exhibited root mean square deviations of 0.46 and 0.49 A, respectively, for the backbone atoms in Cys(4)-Arg(40). Both structures have identical conformations, and they contain a short antiparallel beta-sheet with an inhibitory cystine-knot (ICK) motif that is distributed widely in the antagonists for voltage-gated ion channels, although tachystatin B does not have neurotoxic activity. The structural homology search provided several peptides with structures similar to that of tachystatin B. However, most of them have the advanced functions such as insecticidal activity, suggesting that tachystatin B may be a kind of ancestor of antimicrobial peptide in the molecular evolutionary history. Tachystatin B also displays a significant structural similarity to tachystatin A, which is member of the tachystatin family. The structural comparison of both tachystatins indicated that Tyr(14) and Arg(17) in the long loop between the first and second strands might be the essential residues for binding to chitin.
authors: Division of Advanced Chemical Biology, Graduate School of Advanced Life Science, Frontier Research Center for Post-Genome Science and Technology, Hokkaido University, Sapporo 001-0021, Japan.
authors: Naoki
authors: N
authors: Fujitani
authors: Takahide
authors: T
authors: Kouno
authors: Taku
authors: T
authors: Nakahara
authors: Kenji
authors: K
authors: Takaya
authors: Tsukasa
authors: T
authors: Osaki
authors: Shun-Ichiro
authors: S
authors: Kawabata
authors: Mineyuki
authors: M
authors: Mizuguchi
authors: Tomoyasu
authors: T
authors: Aizawa
authors: Makoto
authors: M
authors: Demura
authors: Shin-Ichiro
authors: S
authors: Nishimura
authors: Keiichi
authors: K
authors: Kawano
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D001665:Binding Sites; D002686:Chitin / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D006737:Horseshoe Crabs / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012996:Solutions; D040681:Structural Homology, Protein
chemical_list: D023181:Antimicrobial Cationic Peptides; D012996:Solutions; C520001:tachystatin B, Tachypleus tridentatus; D002686:Chitin; D003545:Cysteine