Disulfide bridge reorganization induced by proline mutations in maurotoxin

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Maurotoxin (MTX) is a scorpion toxin from Scorpio maurus palmatus.
• MTX belongs to a family of toxins acting on potassium channels.
• MTX possesses a unique disulfide bridge arrangement compared to related toxins like Pi1 and HsTx1.

Purpose of the Study:

• To investigate the effect of specific proline residue substitutions in MTX.
• To determine if these substitutions alter the disulfide bridge organization.
• To evaluate the impact on MTX's pharmacological activity on potassium channels.

Main Methods:

• Site-directed mutagenesis was used to substitute proline residues at positions 12 and/or 20 in MTX.
• The disulfide bridge pairings of the resulting analog ([A(12),A(20)]MTX) were analyzed.
• Pharmacological assays were performed on Shaker B, rat Kv1.2, and rat Kv1.3 channels.

Main Results:

• Substitution of proline residues resulted in a conventional disulfide bridge arrangement, similar to Pi1 and HsTx1.
• The overall three-dimensional structure of the MTX analog remained largely unchanged.
• [A(12),A(20)]MTX retained potent blocking activity on Shaker B and rat Kv1.2 channels.
• The MTX analog became inactive on rat Kv1.3 channels.

Conclusions:

• Discrete point mutations in MTX can induce significant reorganization of disulfide bridge pairings.
• These structural changes are associated with a distinct pharmacological profile.
• MTX analogs offer a valuable tool for understanding structure-activity relationships in potassium channel toxins.