Emerging bacterial resistance against current antibiotics is a growing concern of the 21st century . Antimicrobial peptides (AMPs), compounds commonly found within all living organisms, are considered promising candidates to fight these resistant pathogens. Many strategies for their optimization have been investigated, one of them being the use of a combination of multiple AMPs, leading to a synergistic effect. Magainin 2 and PGLa are AMPs present in the skin of African clawed frog Xenopus laevis and were shown to exhibit this synergistic activity against various Gram-negative bacteria .
The original studies, both experimental and computational, lead to the conclusion that the mechanism of action by magainin 2 with PGLa was based solely on the formation of toroidal pores in the bacterial membranes [2-4]. Here we present recent evidence showing the two peptides promote adhesion and aggregation of lipid membranes. We achieved the results via a combination of modern techniques: coarse-grained computer simulations on model lipid bilayers, cryogenic electron microscopy, small angle X-ray scattering, and fluorescence confocal microscopy using lipid vesicles . Additionally, we performed super-resolution lattice structured illumination microscopy on E.coli.
Our results do not fit with the current model of the synergistic action by magainin 2 and PGLa, represented by a formation of toroidal transmembrane pores. A novel model will be required to explain the previous observations of membrane disruption, specific peptide alignment from nuclear magnetic resonance spectroscopy, together with the membrane adhesion and fusion we observed.
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2. K. Matsuzaki et al., Biochemistry, 37, (1998).
3. P. Tremouilhac, E. Strandberg, P. Wadhwani, and A. S. Ulrich, Journal of Biological Chemistry, 281, (2006).
4. J. Zerweck et al., Scientific Reports, 7, (2017).
5. I. Kabelka et al, Biophysical Journal, (2022).
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 101001470) and from the Czech Science Foundation (project no. GA20-20152S). Computational resources were provided by the CESNET LM2015042 and the CERIT Scientific Cloud LM2015085 provided under the program Projects of Large Research, Development, and Innovations Infrastructures. Additional computational resources were obtained from IT4 Innovations National Super-computing Center – LM2015070 project supported by MEYS CR from the Large Infrastructures for Research, Experimental Development and Innovations. We acknowledge the core facility CELLIM supported by MEYS CR (LM2018129 Czech-BioImaging). We acknowledge Cryo-electron microscopy and tomography core facility CEITEC MU of CIISB, Instruct-CZ Centre supported by MEYS CR (LM2018127).