Poster abstracts
Poster number 20 submitted by Jayod Kariyawasam
Challenging the Cationic Paradigm: Structural and Functional Studies of Oncocin–Ribosome Interactions
Jayod Kariyawasam (Chemistry , Wayne State University), Teresa Wolak (Chemistry , Wayne State University), Joseph Simbeni (Chemistry, Wayne State University), Stella Rodriguez (Biology, University of Detroit Mercy), Hien M. Nguyen (Chemistry, Wayne State University), Christine S. Chow (Chemistry, Wayne State University)
Abstract:
Antimicrobial resistance (AMR) is one of the major health concerns in the world, requiring urgent therapeutic solutions. Among different approaches, antimicrobial peptides (AMPs) represent a key component in the fight against AMR. Proline-rich antimicrobial peptides (PrAMPs), owing to their high proline content, have shown greater inhibitory potential against the Gram-negative bacterial strains. Among these PrAMPs, oncocin is of particular interest as it inhibits protein synthesis by blocking the peptidyl transferase center and the peptide exit tunnel of bacterial ribosomes. Despite the promising features of oncocin, the role of specific amino acid positions in its activity and optimization remains poorly understood. To address this gap, we are using a plasmid-based AMP expression system to analyze the activity of different variants of oncocin in Escherichia coli. We generated a small library of oncocin variants by substituting a single proline residue with all 20 amino acids. Among these variants, an amino acid with anionic properties exhibited improved antimicrobial activity compared to proline, deviating from the canonical cationic profile generally observed in AMPs. Building on this observation, we introduced all possible codons at the modified position and simultaneously truncated the C terminus of oncocin to evaluate both the anionic substitution, codon preference, and peptide length in relation to antimicrobial activity. The antibacterial activity of each mutant peptide was evaluated by growth assays, and the structural and mechanistic impacts were assessed through molecular docking studies. To model oncocin binding in E. coli, we performed structural alignment with the available oncocin–Thermus thermophilus ribosome complex. Overall, our study explores the structure-functional relationships of oncocin variants through a multidisciplinary approach, aiming to overcome current challenges in designing more potent AMPs.
Keywords: Antimicrobial peptides, Oncocin, Ribosome binding