BPS2026 – Direct visualization of maximin 3-induced membrane defects via atomic force microscopy

The interactions between proteins and lipid membranes are fundamental in biology. Antimicrobial peptides (AMPs) are a class of small peptides that are an important part of the innate immune system and have become an area of interest for scientists with therapeutics and drug delivery. This study focuses on the AMP maximin 3, which is derived from the skin secretions of Bombina maxima. Maximin 3 is a 27-amino acid cationic peptide that has strong activity against many bacterial and viral microbes. While prior biochemical studies on this peptide demonstrate its antimicrobial activity and selectivity, there are little data that visualize these interactions at the single molecule level. To accomplish this, we employ atomic force microscopy (AFM), a powerful technique for studying the dynamics of single-molecule systems, including protein-lipid interactions in near-native conditions. Here, we acquired AFM images of maximin 3 with supported DOPC bilayers, which exhibited membrane deformations such as pore formation. Force spectroscopy assays, such as lipid punch-through experiments, demonstrated a shift in mechanical properties of the membrane, such as the yield force. Complementing our AFM results we performed molecular dynamics (MD) simulations to visualize maximin 3-DOPC interactions at the atomic scale and extract energetic information about the peptide’s binding. Taken together, these results provide a real-time, quantitative analysis of maximin 3-induced defects in supported lipid bilayers, highlighting their membrane-permeabilizing ability.