Conjugation of a magainin analogue with lipophilic acids controls hydrophobicity, solution assembly, and cell selectivity

Biochemistry. 2002 Feb 19;41(7):2254-63. doi: 10.1021/bi011549t.

Abstract

Our basic understanding of how to combat fungal infections has not kept pace with the recent sharp rise in life-threatening cases found particularly among immuno-compromised individuals. Current investigations for new potential antifungal agents have focused on antimicrobial peptides, which are used as a cell-free defense mechanism in all organisms. Unfortunately, despite their high antibacterial activity, most of them are not active toward fungi, the reason of which is not clear. Here, we present a new approach to modify an antibacterial peptide, a magainin analogue, to display antifungal activity by its conjugation with lipophilic acids. This approach has the advantage of producing well-defined changes in hydrophobicity, secondary structure, and self-association. These modifications were characterized in solution at physiological concentrations using CD spectroscopy, tryptophan fluorescence, and analytical ultracentrifugation. In order of increasing hydrophobicity, the attachment to the magainin-2 analogue of (i) heptanoic acid results in a monomeric, unordered structure, (ii) undecanoic acid yields concentration-dependent oligomers of alpha helices, and (iii) palmitic acid yields concentration-independent alpha-helical monomers, a novel lipopeptide structure, which is resistant to proteolytic digestion. Membrane-lipopeptide interactions and the membrane-bound structures were studied using fluorescence and ATR-FTIR in PC/PE/PI/ergosterol (5/2.5/2.5/1, w/w) SUV, which constitute the major components of Candida albicans bilayers. A direct correlation was found between oligomerization of the lipopeptides in solution and potent antifungal activity. These results provide insight to a new approach of modulating hydrophobicity and self-assembly of antimicrobial peptides in solution, without altering the sequence of the peptidic chain. These studies also provide a general means of developing a new group of lipopeptide candidates as therapeutic agents against fungal infections.

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Antifungal Agents / chemical synthesis
  • Antifungal Agents / chemistry*
  • Antifungal Agents / metabolism
  • Antifungal Agents / pharmacology
  • Antimicrobial Cationic Peptides / chemical synthesis
  • Antimicrobial Cationic Peptides / chemistry*
  • Antimicrobial Cationic Peptides / metabolism
  • Antimicrobial Cationic Peptides / pharmacology
  • Circular Dichroism
  • Cryptococcus neoformans / drug effects
  • Endopeptidase K / pharmacology
  • Energy Transfer
  • Erythrocyte Membrane / drug effects
  • Fatty Acids / chemistry*
  • Hemolysis / drug effects
  • Heptanoic Acids / chemistry
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Lipid Bilayers / chemistry
  • Lipoproteins / metabolism
  • Magainins
  • Membrane Lipids / metabolism
  • Membrane Potentials / drug effects
  • Molecular Sequence Data
  • Palmitic Acid / chemistry
  • Phospholipids / chemistry
  • Phospholipids / metabolism
  • Protein Structure, Secondary
  • Solutions
  • Spectrometry, Fluorescence
  • Spectroscopy, Fourier Transform Infrared
  • Trypsin / pharmacology
  • Tryptophan / metabolism
  • Ultracentrifugation
  • Xenopus Proteins*
  • Xenopus laevis

Substances

  • Antifungal Agents
  • Antimicrobial Cationic Peptides
  • Fatty Acids
  • Heptanoic Acids
  • Lipid Bilayers
  • Lipoproteins
  • Magainins
  • Membrane Lipids
  • Phospholipids
  • Solutions
  • Xenopus Proteins
  • magainin 2 peptide, Xenopus
  • undecanoic acid
  • Palmitic Acid
  • Tryptophan
  • Trypsin
  • Endopeptidase K