Mapping Protein-Protein Interactions of the Resistance-Related Bacterial Zeta Toxin-Epsilon Antitoxin Complex (ε₂ζ₂)
María Isabel Fernández-Bachiller1, Iwona Brzozowska2, Norbert Odolczyk3
1Institute of Pharmacy, Pharmaceutical and Medicinal Chemistry, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany. isabelfernandezb77@yahoo.es.
Abstract:
Toxin-antitoxin systems constitute a native survival strategy of pathogenic bacteria and thus are potential targets of antibiotic drugs. Here, we target the Zeta-Epsilon toxin-antitoxin system, which is responsible for the stable maintenance of certain multiresistance plasmids in Gram-positive bacteria. Peptide ligands were designed on the basis of the ε₂ζ₂ complex. Three α helices of Zeta forming the protein-protein interaction (PPI) site were selected and peptides were designed conserving the residues interacting with Epsilon antitoxin while substituting residues binding intramolecularly to other parts of Zeta. Designed peptides were synthesized with an N-terminal fluoresceinyl-carboxy-residue for binding assays and provided active ligands, which were used to define the hot spots of the ε₂ζ₂ complex. Further shortening and modification of the binding peptides provided ligands with affinities <100 nM, allowing us to determine the most relevant PPIs and implement a robust competition binding assay.
Insights
Researchers designed peptide ligands targeting the Zeta-Epsilon toxin-antitoxin system, crucial for antibiotic resistance in bacteria. These peptides successfully identified key interactions, paving the way for new antibiotic drug development.
Area of Science:
- Microbiology
- Molecular Biology
- Drug Discovery
Background:
- Toxin-antitoxin systems are bacterial survival mechanisms and potential antibiotic targets.
- The Zeta-Epsilon system maintains multiresistance plasmids in Gram-positive bacteria.
Purpose of the Study:
- To design and characterize peptide ligands targeting the Zeta-Epsilon toxin-antitoxin complex.
- To identify critical protein-protein interactions within the complex for potential drug development.
Main Methods:
- Peptide design based on the ε₂ζ₂ complex structure, focusing on protein-protein interaction (PPI) sites.
- Synthesis of fluorescein-labeled peptides for binding assays.
- Affinity determination and competition binding assays to identify hot spots and relevant PPIs.
Main Results:
- Designed peptides acted as active ligands for the ε₂ζ₂ complex.
- Identified key residues and interactions constituting the hot spots of the complex.
- Achieved high-affinity ligands (<100 nM) through peptide optimization.
Conclusions:
- Peptide ligands can effectively target bacterial toxin-antitoxin systems.
- This study provides a foundation for developing novel antibiotics targeting plasmid maintenance mechanisms.
- The identified hot spots are crucial for understanding and disrupting the Zeta-Epsilon system.
