1wmt
From Proteopedia
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Scorpion toxin (IsTX) from Opisthacanthus madagascariensis
Overview
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.
About this Structure
1WMT is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
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
Page seeded by OCA on Wed Nov 21 05:32:15 2007
