Charge and aggregation pattern govern the interaction of plasticins with LPS monolayers mimicking the external leaflet of the outer membrane of Gram-negative bacteria

• Published in: Biochimica et biophysica acta Vol. 1848; no. 11; pp. 2967 - 2979
• Main Authors: Michel, J.P., Wang, Y.X., Dé, E., Fontaine, P., Goldmann, M., Rosilio, V.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2015; Elsevier
• Subjects: Cell Membrane - chemistry; Cell Membrane - metabolism; Chemical Sciences; Circular Dichroism; Condensed Matter; Eye Proteins - chemistry; Eye Proteins - metabolism; Gram-negative bacteria; Gram-Negative Bacteria - chemistry; Gram-Negative Bacteria - metabolism; Grazing incidence X-ray diffraction, Atomic force microscopy; Life Sciences; Lipopolysaccharide; Lipopolysaccharides - chemistry; Lipopolysaccharides - metabolism; Liposome; Liposomes - chemistry; Liposomes - metabolism; Membrane Lipids - chemistry; Membrane Lipids - metabolism; Microscopy, Atomic Force; Monolayer; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - metabolism; Phospholipids - chemistry; Phospholipids - metabolism; Physics; Plasticin; Protein Binding; Salmonella enterica - chemistry; Salmonella enterica - metabolism; Soft Condensed Matter; Static Electricity; X-Ray Diffraction; CD; Monolayer; PMB; AFM; Liposome; CL; DLS; Plasticin; Grazing incidence X-ray diffraction, Atomic force microscopy; LPS; BAM; GIXD; S-LPS; PDI; SOPG; PLs; SOPE; LC; Kdo; FWHM; Lipopolysaccharide; LE; Gram-negative bacteria; OM
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/j.bbamem.2015.09.005

Bacterial resistance to antibiotics has become today a major public health issue. In the development of new anti-infectious therapies, antimicrobial peptides appear as promising candidates. However, their mechanisms of action against bacterial membranes are still poorly understood. We describe for the first time the interaction and penetration of plasticins into lipid monolayers and bilayers modeling the two leaflets of the asymmetrical outer membrane of Gram-negative bacteria. The lipid composition of these monolayers mimics that of each leaflet: mixtures of LPS Re 595 mutant and wild type S-form from Salmonella enterica for the external leaflet, and SOPE/SOPG/cardiolipin (80/15/5) for the inner one. The analysis of the interfacial behavior of native (PTCDA1) and modified (PTCDA1-KF) antimicrobial plasticins showed that PTCDA1-KF exhibited better surface properties than its unmodified counterpart. Both peptides could penetrate into the model monolayers at concentrations higher than 0.1μM. The penetration was particularly enhanced for PTCDA1-KF into the mixed LPS monolayer, due to attractive electrostatic interactions. Grazing X-ray diffraction and atomic force microscopy studies revealed the changes in LPS monolayers organization upon peptide insertion. The interaction of plasticins with liposomes was also monitored by light scattering and circular dichroism techniques. Only the cationic plasticin achieved full disaggregation and structuration in α helices, whereas the native one remained aggregated and unstructured. The main steps of the penetration mechanism of the two plasticins into lipid models of the external leaflet of the outer membrane of Gram-negative bacteria have been established. [Display omitted] •The initial steps of plasticins interaction with bacterial membranes were analyzed.•LPS monolayers mimic the external leaflet of Gram-negative bacteria outer membrane.•The charge, conformation and aggregation state were the relevant peptide parameters.•Only the active plasticin penetrated and disorganized the LPS monolayer structure.