Refined solution structure of the anti-mammal and anti-insect LqqIII scorpion toxin: Comparison with other scorpion toxins
✍ Scribed by Céline Landon; Patrick Sodano; Bruno Cornet; Jean-Marc Bonmatin; Charles Kopeyan; Hervé Rochat; Françoise Vovelle; Marius Ptak
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 654 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0887-3585
No coin nor oath required. For personal study only.
✦ Synopsis
The solution structure of the anti-mammal and anti-insect LqqIII toxin from the scorpion Leiurus quinquestriatus quinquestriatus was refined and compared with other long-chain scorpion toxins. This structure, determined by 1 H-NMR and molecular modeling, involves an a-helix (18-29) linked to a threestranded b-sheet (2-6, 33-39, and 43-51) by two disulfide bridges. The average RMSD between the 15 best structures and the mean structure is 0.71 Å for Ca atoms. Comparison between LqqIII, the potent anti-mammal AaHII, and the weakly active variant-3 toxins revealed that the LqqIII three-dimensional structure is closer to that of AaHII than to the variant-3 structure. Moreover, striking analogies were observed between the electrostatic and hydrophobic potentials of LqqIII and AaHII. Several residues are well conserved in long-chain scorpion toxin sequences and seem to be important in protein structure stability and function. Some of them are involved in the CSab (Cysteine Stabilized a-helix b-sheet) motif. A comparison between the sequences of the RII rat brain and the Drosophila extracellular loops forming scorpion toxin binding-sites of Na 1 channels displays differences in the subsites interacting with anti-mammal or anti-insect toxins. This suggests that hydrophobic as well as electrostatic interactions are essential for the binding and specificity of long-chain scorpion toxins.