Scorpions toxins

Scorpions use a cocktail of toxins to immobilize their prey. Their venoms c onstitute a complex mixure of polypeptides exhibiting different pharmacolog ical activities. These polypeptides are small (between 30 and 70 amino acid s long), basic and highly reticulated (3 or 4 disulfide bridges). They bind with very high affinities to specific targets, which are different ionic c hannels of excitable cells. Thus, they constitute usefull tools for the neu robiologist. 1)The a long << chain toxins >> (60-70 amino acids residues cross-linked by 3 disulfide-bridges) affect exclusively voltage-dependent Na; channels of excitable cells from mammals and insects; 2) The << short chain toxins >> (30-40 amino acids residues cross-linked by 3 or 4 disulfide-bridges) block several types of K+ channels in different cells. At the structural level, scorpion toxins show a dense core of secondary ele ments, 2 1/2 turns of an alpha-helix, and a short segment of anti-parallel beta-sheet, already found in all known structures of scorpion toxins, irres pective of their size. sequence and function. From cDNA libraries, full-lengh cDNAs encoding precursors of these toxins h ave been isolated and could be used in heterologous expression systems, in order to produce recombinant toxins. They will provide a template for the d esign of new biopesticide agents, able to mimic the interactive surface of the toxins.