Three-dimensional model of the insect-directed scorpion toxin from Androctonus australis Hector and its implication for the evolution of scorpion toxins in general.
The three-dimensional structure of the insect-directed toxin from the scorpion Androctonus australis Hector has been modelled using computer graphics and energy-minimization techniques. The model-building procedure was based on the known high resolution structures of two scorpion toxins of different types: toxin II from A. australis Hector, an alpha-toxin, and variant 3 from Centruroides sculpturatus Ewing that belongs to the beta-toxin structural group. Although the insect-directed toxin has one atypical disulfide bridge, the general structural features of the scorpion toxin family, including the presence of a "conserved-hydrophobic" surface, seem to be well-conserved. However, the orientation and length of some loops and regions thought to be important for toxicity are different for alpha-toxins, beta-toxins, and the insect-directed toxin. Thus, the binding of a scorpion toxin to its site on the Na+ channel seems to be based on (1) the presence of a surface containing a series of conserved and/or hydrophobic residues, more or less common to all these molecules, and (2) an adjacent area that modulates the specificity of the interaction.
Fontecilla-Camps
J C
JC
Laboratoire de Cristallographie et de Cristallisation de Macromolécules Biologiques, U.R.A. 232, CNRS, Faculté de Médecine, Marseille, France.
D000595:Amino Acid Sequence; D000818:Animals; D003461:Crystallography; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012604:Scorpion Venoms; D012605:Scorpions / Q000235:genetics
D012604:Scorpion Venoms