Loop Replacement Enhances the Ancestral Antibacterial Function of a Bifunctional Scorpion Toxin

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Scorpion toxins targeting potassium channels (KTxs) share evolutionary links with antibacterial defensins.
• Some KTXs exhibit weak inhibitory activity against both potassium channels and bacteria, indicating bifunctional potential.
• The carboxyl loop region is a key structural element differentiating these protein families.

Purpose of the Study:

• To enhance the antibacterial activity of a bifunctional KTx through protein engineering.
• To investigate the feasibility of modifying scorpion venom peptides for improved antimicrobial applications.
• To explore the potential of ancestral protein function reconstruction.

Main Methods:

• Protein engineering was employed to modify a bifunctional KTx.
• The carboxyl loop of the KTx was substituted with the structurally equivalent loop from defensins.
• The engineered peptide (MeuTXKα3-KFGGI) was synthesized and its antibacterial activity was evaluated.

Main Results:

• The engineered peptide MeuTXKα3-KFGGI demonstrated significantly enhanced antibacterial activity, particularly against Gram-positive bacteria.
• Activity was observed against several antibiotic-resistant opportunistic pathogens.
• The antibacterial spectrum of the engineered peptide was broader compared to the unmodified toxin.

Conclusions:

• Protein engineering by substituting the carboxyl loop can effectively enhance the antibacterial activity of bifunctional scorpion venom peptides.
• This strategy provides a novel method for developing potent antimicrobial agents derived from natural toxins.
• The findings suggest potential applications in engineering other proteins to restore or enhance ancestral functions.