Prokaryotic selectivity and LPS-neutralizing activity of short antimicrobial peptides designed from the human antimicrobial peptide LL-37.
Nan. Yong Hai YH; Bang. Jeong-Kyu JK; Jacob. Binu B; Park. Il-Seon IS; Shin. Song Yub SY
Key Findings
- Shortened LL‑37 fragments can keep antimicrobial and toxin‑neutralizing functions if hydrophobicity is tuned correctly.
- Replacing phenylalanine with tryptophan at the amphipathic interface (a4‑W2) boosts LPS‑neutralizing activity while preserving bacterial selectivity, achieving 2.8‑fold better selectivity than native LL‑37.
- The analog a4‑W2 shows the best combination of bacterial killing selectivity and endotoxin neutralization among the tested peptides, making it a strong template for future therapies.
Practical Outcomes
- For now, there’s no direct protocol you can use—these peptides aren’t available as supplements and need further testing. However, the study highlights that tweaking peptide hydrophobicity and specific amino‑acid swaps can dramatically improve safety and effectiveness, which may guide future DIY peptide designs or inform which emerging products to watch for.
Summary
Scientists tweaked a short piece of the human immune peptide LL-37 and found a version (a4‑W2) that kills bacteria well while also neutralizing harmful bacterial toxins, without losing its safety profile. The key was adjusting how water‑loving and fat‑loving parts of the peptide are balanced and swapping a phenylalanine for a tryptophan at a specific spot. This work points to a promising new drug candidate for infections and septic shock, but it’s still early‑stage research.
Abstract
To develop novel antimicrobial peptides (AMPs) with shorter lengths, improved prokaryotic selectivity and retained lipolysaccharide (LPS)-neutralizing activity compared to human cathelicidin AMP, LL-37, a series of amino acid-substituted analogs based on IG-19 (residues 13-31 of LL-37) were synthesized. Among the IG-19 analogs, the analog a4 showed the highest prokaryotic selectivity, but much lower LPS-neutralizing activity compared to parental LL-37. The analogs, a5, a6, a7 and a8 with higher hydrophobicity displayed LPS-neutralizing activity comparable to that of LL-37, but much lesser prokaryotic selectivity. These results indicate that the proper hydrophobicity of the peptides is crucial to exert the amalgamated property of LPS-neutralizing activity and prokaryotic selectivity. Furthermore, to increase LPS-neutralizing activity of the analog a4 without a remarkable decrease in prokaryotic selectivity, we synthesized Trp-substituted analogs (a4-W1 and a4-W2), in which Phe(5) or Phe(15) of a4 is replaced by Trp. Despite their same prokaryotic selectivity, a4-W2 displayed much higher LPS-neutralizing activity compared to a4-W1. When compared with parental LL-37, a4-W2 showed retained LPS-neutralizing activity and 2.8-fold enhanced prokaryotic selectivity. These results suggest that the effective site for Trp-substitution when designing novel AMPs with higher LPS-neutralizing activity, without a remarkable reduction in prokaryotic selectivity, is the amphipathic interface between the end of the hydrophilic side and the start of the hydrophobic side rather than the central position of the hydrophobic side in their α-helical wheel projection. Taken together, the analog a4-W2 can serve as a promising template for the development of therapeutic agents for the treatment of endotoxic shock and bacterial infection.
Study Information
pubmed
2012
2012-04-10T00:00:00.000Z
10.1016/j.peptides.2012.04.004
72
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