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Sequence context induced antimicrobial activity: insight into lipopolysaccharide permeabilization.

Anirban Ghosh1, Aritreyee Datta, Jagannath Jana

  • 1Biomolecular NMR and Drug Design Laboratory, Department of Biophysics, Bose Institute, P-1/12 CIT Scheme VII (M), Kolkata 700054, India. subhro_c@jcbose.ac.in bhunia@jcbose.ac.in.

Molecular Biosystems
|April 10, 2014
PubMed
Summary

Lactoferrampin (WR17) effectively targets Gram-negative bacteria outer membranes and neutralizes endotoxins. Its N-terminal helix inserts into lipopolysaccharide (LPS) micelles, while the C-terminal motif anchors it, revealing its antimicrobial mechanism.

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Area of Science:

  • Biochemistry
  • Microbiology
  • Structural Biology

Background:

  • Lactoferrampin (WR17) exhibits potent antibacterial and candidacidal activities.
  • The mechanism by which WR17 interacts with Gram-negative bacterial outer membranes and neutralizes endotoxins remains unelucidated.

Purpose of the Study:

  • To elucidate the mechanism of WR17's interaction with lipopolysaccharide (LPS) and its role in antimicrobial activity and endotoxin neutralization.
  • To characterize the structural basis of WR17's activity using biophysical and computational methods.

Main Methods:

  • Antimicrobial activity assays, calcein leakage assays, NPN dye uptake assays, and endotoxin neutralization assays.
  • High-resolution Nuclear Magnetic Resonance (NMR) spectroscopy to determine WR17 structure in LPS.
  • In silico molecular modeling and Molecular Dynamics (MD) simulations.
  • Isothermal titration calorimetry (ITC) and fluorescence spectroscopy (anisotropy, red edge excitation shift assay).

Main Results:

  • The N-terminal region (Trp1-Phe11) of WR17 forms a helix and inserts into LPS micelles at a 45° angle.
  • The C-terminal region (Lys13-Arg17) remains a flexible random coil, with the K(13)xK(15)xR(17) motif facilitating LPS incorporation.
  • NMR and fluorescence data revealed motional restriction of Trp1 within the LPS micelle, with an insertion depth of approximately 7 Å.
  • ITC indicated an endothermic interaction between WR17 and LPS.

Conclusions:

  • WR17's sequence context modulates its antimicrobial and anti-endotoxic activities.
  • The N-terminal helix and C-terminal anchoring motif are crucial for WR17's interaction with LPS and membrane permeabilization.
  • The identified K(13)NKSR(17) motif provides a basis for designing novel anti-endotoxic molecules.