Structure-function relationships of scorpion neurotoxins

Area of Science:

• Biochemistry
• Toxicology
• Molecular Biology

Background:

• Scorpion venoms contain potent toxins that target ion channels.
• Understanding the structure-activity relationship of these toxins is crucial for developing effective antivenoms and therapeutics.

Purpose of the Study:

• To investigate the role of specific amino acid residues in the toxic and antigenic activities of toxins I, II, and III from the scorpion Androctonus australis Hector.
• To identify key residues involved in the active and antigenic sites of these toxins through chemical modification.

Main Methods:

• Chemical modification of trifunctional amino acid residues (disulfide bridges, tryptophan, carboxylates, lysine, tyrosine, histidine) in scorpion toxins.
• Assessing the impact of modifications on toxic activity through functional assays.
• Evaluating changes in antigenic activity following chemical modifications.

Main Results:

• Disulfide bridge reduction/methylation and modification of five carboxylates in toxin II abolished toxicity.
• Acetylation of lysine and tyrosine residues in toxin II eliminated both toxic and antigenic activity, with partial restoration of antigenicity by hydroxylamine treatment.
• Citraconylation of toxins II and III led to complete toxicity loss, reversible by decitraconylation.
• Alkylation with iodoacetic acid indicated lysine modification as the primary cause of toxicity loss in toxin II and toxin I.

Conclusions:

• Specific lysine and carboxylate residues are essential for the toxic activity of scorpion toxin II.
• Tyrosine residues are involved in the antigenic sites of toxin II.
• Chemical modification provides insights into the structure-function relationships of scorpion toxins, aiding in antivenom development.