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==The solution structure of horseshoe crab antimicrobial peptide tachystatin b with the inhibitory cystine-knot motif==
<StructureSection load='2dcw' size='340' side='right'caption='[[2dcw]]' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2dcw]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Tachypleus_tridentatus Tachypleus tridentatus]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2DCW OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2DCW FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Solution NMR, 20 models</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=2dcw FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2dcw OCA], [https://pdbe.org/2dcw PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2dcw RCSB], [https://www.ebi.ac.uk/pdbsum/2dcw PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2dcw ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/TACB2_TACTR TACB2_TACTR] Exhibits stronger antimicrobial activity against the Gram-positive bacteria (S.aureus (IC(50) is 7.4 ug/ml)) and fungi (C.albicans (IC(50) is 3.0 ug/ml) and P.pastoris (IC(50) is 0.1 ug/ml)) than Gram-negative bacteria (E.coli no inhibition at 100 ug/ml). Binds to chitin (4.3 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.
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== Publication Abstract from PubMed ==
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.

The solution structure of horseshoe crab antimicrobial peptide tachystatin B with an inhibitory cystine-knot motif.,Fujitani N, Kouno T, Nakahara T, Takaya K, Osaki T, Kawabata S, Mizuguchi M, Aizawa T, Demura M, Nishimura S, Kawano K J Pept Sci. 2007 Apr;13(4):269-79. PMID:17394123<ref>PMID:17394123</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Tachypleus tridentatus]]
[[Category: Fujitani N]]
[[Category: Kawano K]]