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Structure-function relationships in histidine-rich antimicrobial peptides from Atlantic cod.

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Antimicrobial peptides (AMPs) Gad-1 and Gad-2 show pH-dependent activity. Optimizing AMPs for therapeutic use requires balancing structural plasticity and amphipathicity, particularly in histidine-rich sequences.

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Antimicrobial Peptides

Background:

  • Gad-1 and Gad-2 are histidine-rich antimicrobial peptides (AMPs).
  • Their activity may be pH-dependent, influencing therapeutic potential.
  • Understanding structure-function relationships is key to improving AMPs.

Purpose of the Study:

  • To investigate the pH-dependent structure-function relationships of Gad-1 and Gad-2.
  • To identify key features for enhancing AMP therapeutic ratios.

Main Methods:

  • Activity assays against Gram-negative bacteria and cancer cell lines.
  • Circular dichroism spectroscopy to assess structural plasticity.
  • High-resolution solution NMR to determine peptide structures in SDS micelles.

Main Results:

  • Gad-2 exhibits enhanced activity at acidic pH compared to neutral pH; Gad-1 shows similar activity across pH ranges.
  • Gad-2 displays greater structural plasticity (helicity changes with pH/lipids) than Gad-1.
  • NMR structures reveal optimal activity depends on a balance of N-terminal mixed structure and amphipathic C-terminal regions.

Conclusions:

  • AMP activity and structural plasticity are influenced by pH and lipid environment.
  • Therapeutic ratio improvement may involve incorporating histidine-pairs and maintaining modest charge and imperfect amphipathicity.