Amino Acid Substitutions in Bacteriocin Lactolisterin BU Reveal Functional Domains Involved in Biological Activity Against Staphylococcus aureus

TL;DR

Scientists modified a natural antimicrobial peptide to better understand how its structure affects its ability to kill bacteria and reduce toxicity.

Contribution

The study identifies key structural domains in lactolisterin BU that influence antimicrobial activity and toxicity through amino acid substitutions.

Findings

Glycine-to-alanine substitutions in helix I enhanced antimicrobial activity but altered toxicity.

Modifications at helix junctions reduced antimicrobial effectiveness.

Sub-MIC treatment differentially regulated virulence genes in Staphylococcus aureus.

Abstract

The emergence of multidrug-resistant pathogens has driven the development of novel antimicrobial peptides (AMPs) as therapeutic alternatives. Lactolisterin LBU (LBU) is a bacteriocin with promising activity against Gram-positive bacteria, including Staphylococcus aureus. In this study, we designed and evaluated a panel of amino acid variants of LBU to investigate domain–activity relationships and improve activity. Peptides were commercially synthesized, and their effect was evaluated for minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), hemolytic activity, cytotoxicity, in vivo toxicity, and virulence modulation. AlphaFold3 structural prediction of LBU revealed a four-helix topology with amphipathic and hydrophobic segments. Helical wheel projections identified helices I and IV as amphipathic, suggesting their potential involvement in membrane interaction and activity. Glycine-to-alanine substitutions at helix I markedly increased antimicrobial activity but altered toxicity profiles. In contrast, changes at helix junctions and kinks reduced antimicrobial activity. We also showed differential regulation of virulence genes upon sub-MIC treatment. Overall, rational substitution enabled identification of residues critical for activity and toxicity, providing insights into therapeutic tuning of lactolisterin-based peptides.

Figures