Horseshoe crab hemocyte-derived antimicrobial polypeptides, tachystatins, with sequence similarity to spider neurotoxins.
Antimicrobial peptides, named tachystatins A, B, and C, were identified from hemocytes of the horseshoe crab Tachypleus tridentatus. Tachystatins exhibited a broad spectrum of antimicrobial activity against Gram-negative and Gram-positive bacteria and fungi. Of these tachystatins, tachystatin C was most effective. Tachystatin A is homologous to tachystatin B, but tachystatin C has no significant sequence similarity to tachystatins A and B. Tachystatins A and B showed sequence similarity to omega-agatoxin-IVA of funnel web spider venom, a potent blocker of voltage-dependent calcium channels. However, they exhibited no blocking activity of the P-type calcium channel in rat Purkinje cells. Tachystatin C also showed sequence similarity to several insecticidal neurotoxins of spider venoms. Tachystatins A, B, and C bound significantly to chitin. A causal relationship was observed between chitin binding activity and antifungal activity. Tachystatins caused morphological changes against a budding yeast, and tachystatin C had a strong cell lysis activity. The septum between mother cell and bud, a chitin-rich region, was stained by fluorescence-labeled tachystatin C, suggesting that the primary recognizing substance on the cell wall is chitin. As horseshoe crab is a close relative of the spider, tachystatins and spider neurotoxins may have evolved from a common ancestral peptide, with adaptive functions.
Osaki
T
T
Department of Molecular Biology, Graduate School of Medical Science, Fukuoka 812-8582, Japan.
Omotezako
M
M
Nagayama
R
R
Hirata
M
M
Iwanaga
S
S
Kasahara
J
J
Hattori
J
J
Ito
I
I
Sugiyama
H
H
Kawabata
S
S
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000187:drug effects* / Q000235:genetics / Q000494:pharmacology; D001483:Base Sequence; D001798:Blood Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D006434:Hemocytes / Q000737:chemistry*; D006737:Horseshoe Crabs / Q000737:chemistry*; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000737:chemistry*; D051381:Rats; D013111:Spider Venoms / Q000737:chemistry*
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D009498:Neurotoxins; D013111:Spider Venoms; C520001:tachystatin B, Tachypleus tridentatus