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THREE-DIMENSIONAL STRUCTURE OF ANTIMICROBIAL PEPTIDE TACHYSTATIN A ISOLATED FROM HORSESHOE CRAB
Structural highlights
FunctionTACA2_TACTR Exhibits stronger antimicrobial activity against the Gram-positive bacteria (S.aureus (IC(50) is 4.2 ug/ml)) and fungi (C.albicans (IC(50) is 3.0 ug/ml) and P.pastoris (IC(50) is 0.5 ug/ml)) than Gram-negative bacteria (E.coli (IC(50) is 25 ug/ml)). Binds to chitin (8.4 uM are required to obtain 50% of binding). Does not cause hemolysis on sheep erythrocytes. Has no blocking activity on the P-type calcium channel. Publication Abstract from PubMedThe 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. Structure of the antimicrobial peptide tachystatin A.,Fujitani N, Kawabata S, Osaki T, Kumaki Y, Demura M, Nitta K, Kawano K J Biol Chem. 2002 Jun 28;277(26):23651-7. Epub 2002 Apr 16. PMID:11959852[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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