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Production and Testing of Antimicrobial Peptides and Their Mimics
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Production and Testing of Antimicrobial Peptides and Their Mimics

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Origin of low mammalian cell toxicity in a class of highly active antimicrobial amphipathic helical peptides

Ayman Hawrani1, Robin A Howe, Timothy R Walsh

  • 1Department of Cellular and Molecular Medicine, Bristol University, Bristol BS8 1TD, United Kingdom.

The Journal of Biological Chemistry
|April 25, 2008
PubMed

Insights

A novel antimicrobial peptide, RTA3, shows reduced toxicity to mammalian cells by not binding well to neutral membranes. This finding offers strategies for developing safer antimicrobial peptides.

Area of Science:

  • Biochemistry
  • Microbiology
  • Molecular Biology

Background:

  • A novel antimicrobial peptide, RTA3, from Streptococcus mitis exhibits potent activity against Gram-negative bacteria with low salt sensitivity and minimal toxicity.
  • RTA3 possesses a positively charged, amphipathic helical structure, but uniquely features a positively charged residue (Arg-5) on its nonpolar face upon membrane binding.

Purpose of the Study:

  • To investigate the role of the positively charged residue on the nonpolar face of RTA3 in minimizing mammalian cell toxicity.
  • To explore the binding interactions of RTA3 and its mutant with neutral and negatively charged membranes.

Main Methods:

  • Comparative analysis of RTA3 and an R5L mutant peptide with varying membrane compositions.
  • Spectroscopic techniques to analyze peptide conformation and membrane binding.
  • Determination of binding constants to neutral and negatively charged lipid bilayers.

Main Results:

  • The R5L mutant peptide exhibited significantly enhanced mammalian cell toxicity compared to wild-type RTA3.
  • Enhanced toxicity of the mutant correlated with increased binding and helical adoption upon interaction with neutral membranes.
  • Wild-type RTA3 demonstrated significantly reduced binding (over 1000-fold decrease) to neutral membranes, while accommodating negative charges without unfolding.
  • Tryptophan residues were identified as crucial for promoting amphipathic helical peptide binding to neutral bilayers.

Conclusions:

  • The presence of a positively charged residue on the nonpolar face of amphipathic helical peptides, like RTA3, is a key factor in reducing eukaryotic cell toxicity.
  • These peptides exhibit poor binding to neutral membranes, characteristic of eukaryotic cell membranes, thus contributing to their safety profile.
  • Understanding these binding specificities provides a strategic approach for designing safer and more effective antimicrobial peptides.

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