Design of Protegrin-1 Analogs with Improved Antibacterial Selectivity

Area of Science:

• Biochemistry
• Microbiology
• Drug Discovery

Background:

• Protegrin-1 (PG-1) is a potent antimicrobial peptide effective against multidrug-resistant pathogens.
• High hemolytic activity and cytotoxicity limit PG-1's therapeutic use.
• Developing safer antimicrobial agents is crucial for combating resistant infections.

Purpose of the Study:

• To design and characterize Protegrin-1 analogs with reduced mammalian cell toxicity while maintaining antimicrobial efficacy.
• To identify specific amino acid substitutions that improve the therapeutic index of PG-1.

Main Methods:

• Rational design of PG-1 analogs by substituting residues in the central β-sheet region to modulate charge and hydrophobicity.
• Production of analogs using thioredoxin fusion in *Escherichia coli*.
• Assessment of antimicrobial activity, hemolytic activity, and cytotoxicity of wild-type PG-1 and its analogs.

Main Results:

• A single amino acid substitution (V16R) in the C-terminal β-strand significantly reduced hemolytic activity without compromising antimicrobial potency.
• The analog [V16R] demonstrated a ≥30-fold improvement in therapeutic index compared to wild-type PG-1.
• FTIR analysis indicated that [V16R] does not form oligomeric structures, unlike wild-type PG-1, in membrane-mimicking environments.

Conclusions:

• The PG-1 analog [V16R] exhibits a favorable safety profile and potent antimicrobial activity, making it a promising lead compound.
• Modulating PG-1's oligomerization through specific substitutions can decouple antimicrobial action from mammalian cell toxicity.
• [V16R] showed efficacy in a murine septicemia model, supporting its potential for systemic antibiotic development.