Antimicrobial Activity and 70S Ribosome Binding of Apidaecin-Derived Api805 with Increased Bacterial Uptake Rate

Area of Science:

• Microbiology
• Biochemistry
• Drug Discovery

Background:

• Rising antimicrobial resistance necessitates novel therapeutic agents.
• Antimicrobial peptides (AMPs), particularly proline-rich AMPs (PrAMPs), offer a promising avenue by targeting bacterial protein translation via the 70S ribosome.

Purpose of the Study:

• To design and characterize a novel designer peptide, Api805, by combining sequences from known PrAMPs.
• To investigate the mechanism of action and bacterial strain-specific activity of Api805.

Main Methods:

• Peptide design and synthesis.
• Bacterial growth inhibition assays against *Escherichia coli* strains.
• Ribosome binding affinity measurements.
• In vitro protein translation inhibition assays.
• Bacterial uptake studies.

Main Results:

• Api805 exhibited differential activity against *E. coli* B and K12 strains, not explained by ribosome binding affinity or SbmA transporter mutations.
• Api805 demonstrated a novel mode of action, inhibiting protein translation independently of release factors, potentially via a multimodal effect.
• Faster and greater uptake of Api805 into *E. coli* B compared to *E. coli* K12 was observed, possibly due to differences in lipopolysaccharide (LPS) core structure.

Conclusions:

• Structural modifications in PrAMPs can significantly alter their ribosomal binding sites and mechanisms of action.
• Api805 represents a new class of antibiotics with a unique mechanism, highlighting the potential for rational design of AMPs.
• Understanding bacterial entry mechanisms, like LPS variations, is crucial for optimizing AMP efficacy.