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Activity of Membrane-Permeabilizing Lpt Peptides.

Stefano Maggi1, Giulia Mori1, Luigi Maglie1

  • 1Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy.

Biomolecules
|August 29, 2024
PubMed
Summary

Toxin-antitoxin peptides Lpt and Lpt-like from Lacticaseibacillus permeabilize bacterial membranes by forming transient lipid pores, not stable peptide pores, impacting cell growth.

Keywords:
Lacticaseibacillusliposome leakagemembrane active peptidesmembrane permeabilizationnucleoid condensationtoxin–antitoxin systemstype I toxins

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Area of Science:

  • Microbiology and Molecular Biology
  • Biochemistry and Biophysics

Background:

  • Type I toxin-antitoxin systems, encoded on plasmid DNA in Lacticaseibacillus strains, utilize peptides like Lpt.
  • These peptides are 29 amino acids long, predicted to have an alpha-helical structure with a hydrophobic core and charged termini.

Purpose of the Study:

  • To investigate the toxicity and membrane-permeabilizing capabilities of Lpt and Lpt-like peptides.
  • To elucidate the mechanism of action of these peptides on bacterial cell membranes.

Main Methods:

  • Expression of Lpt and Lpt-like peptides in E. coli to observe cellular effects.
  • Liposome leakage assays, dynamic light scattering, and circular dichroism (CD) spectroscopy to evaluate membrane interaction.
  • Analysis of peptide structural changes upon liposome interaction.

Main Results:

  • Lpt and Lpt-like peptides induced growth arrest, nucleoid condensation, and cell membrane damage in E. coli.
  • Peptides caused liposome leakage dependent on concentration, without complete liposome disruption.
  • Peptide activity was influenced by liposome size and negative charge (PCPS), and peptides lost alpha-helical structure upon membrane interaction.

Conclusions:

  • Lpt and Lpt-like peptides act by transiently disrupting the membrane permeability barrier, likely forming "lipid pores".
  • The mechanism differs from typical membrane-active peptides that form stable pores.
  • Peptide structural destabilization upon membrane interaction is a key feature of their activity.