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==Scorpion toxin (IsTX) from Opisthacanthus madagascariensis==
<StructureSection load='1wmt' size='340' side='right'caption='[[1wmt]]' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1wmt]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Opisthacanthus_madagascariensis Opisthacanthus madagascariensis]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1WMT OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1WMT 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=1wmt FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1wmt OCA], [https://pdbe.org/1wmt PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1wmt RCSB], [https://www.ebi.ac.uk/pdbsum/1wmt PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1wmt ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/KAX6B_OPIMA KAX6B_OPIMA] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The novel sex-specific potassium channel inhibitor IsTX, a 41-residue peptide, was isolated from the venom of male Opisthacanthus madagascariensis. Two-dimensional NMR techniques revealed that the structure of IsTX contains a cysteine-stabilized alpha/beta-fold. IsTX is classified, based on its sequential and structural similarity, in the scorpion short toxin family alpha-KTx6. The alpha-KTx6 family contains a single alpha-helix and two beta-strands connected by four disulfide bridges and binds to voltage-gated K(+) channels and apamin-sensitive Ca(2+)-activated K(+) channels. The three-dimensional structure of IsTX is similar to that of Heterometrus spinifer toxin (HsTX1). HsTX1 blocks the Kv1.3 channel at picomolar concentrations, whereas IsTX has much lower affinities (10 000-fold). To investigate the structure-activity relationship, the geometry of sidechains and electrostatic surface potential maps were compared with HsTX1. As a result of the comparison of the primary structures, Lys27 of IsTX was conserved at the same position in HsTX1. The analogous Lys23 of HsTX1, the most critical residue for binding to potassium channels, binds to the channel pore. However, IsTX has fewer basic residues to interact with acidic channel surfaces than HsTX1. MALDI-TOF MS analysis clearly indicated that IsTX was found in male scorpion venom, but not in female. This is the first report that scorpion venom contains sex-specific compounds.

Solution structure of IsTX. A male scorpion toxin from Opisthacanthus madagascariensis (Ischnuridae).,Yamaji N, Dai L, Sugase K, Andriantsiferana M, Nakajima T, Iwashita T Eur J Biochem. 2004 Oct;271(19):3855-64. PMID:15373831<ref>PMID:15373831</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 1wmt" style="background-color:#fffaf0;"></div>

==See Also==
*[[Potassium channel toxin 3D structures|Potassium channel toxin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Opisthacanthus madagascariensis]]
[[Category: Andriantsiferana M]]
[[Category: Dai L]]
[[Category: Iwashita T]]
[[Category: Nakajima T]]
[[Category: Sugase K]]
[[Category: Yamaji N]]