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Scorpion toxins specific for Na+-channels.
L D Possani1, B Becerril, M Delepierre
1Department of Molecular Recognition and Structural Biology, Institute of Biotechnology, National Autonomous University of Mexico, Avenida Universidad 2001, Cuernavaca, Mexico. Possani@ibt.unam.mx
European Journal of Biochemistry
|September 22, 1999
Summary
Scorpion toxins are peptides that modulate sodium (Na+) channel function by affecting activation or inactivation. This review classifies these toxins and explores their structure-activity relationships.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Scorpion toxins are small peptides (60-76 amino acids) stabilized by four disulfide bridges.
- These toxins possess a conserved structural motif comprising alpha-helices and beta-sheets, crucial for their function.
- They act as potent modulators of voltage-gated sodium channels, influencing gating kinetics.
Purpose of the Study:
- To review the known sequences and structures of Na+-channel specific scorpion toxins.
- To propose a classification system for these toxins based on functional and structural characteristics.
- To investigate the structure-activity relationships, identifying potential active sites involved in channel binding.
Main Methods:
- Sequence analysis of 85 distinct scorpion toxin peptides.
- Structural determination using X-ray diffraction and NMR spectroscopy for some toxins.
- Physiological experiments to assess toxin effects on Na+-channel gating kinetics (activation and inactivation).
Main Results:
- A conserved structural motif (alpha-helix and beta-sheet) is present in all studied toxins.
- Toxins are classified into 10 groups based on functional and structural features, including alpha-toxins (inactivation) and beta-toxins (activation).
- Species specificity in toxin action is observed, with some toxins affecting channels from mammals, insects, or crustaceans.
Conclusions:
- Scorpion toxins exhibit diverse functional roles and species specificity, making them valuable tools for studying Na+-channel function.
- Specific regions, including charged residues in turns and terminal segments, are implicated in toxin activity.
- Challenges in gene expression hinder the production of active toxins for detailed binding site analysis.