Conjugation of a magainin analogue with lipophilic acids controls hydrophobicity, solution assembly, and cell selectivity.
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.
Avrahami
Dorit
D
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100 Israel.
Shai
Yechiel
Y
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000935:Antifungal Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D002942:Circular Dichroism; D003455:Cryptococcus neoformans / Q000187:drug effects; D019286:Endopeptidase K / Q000494:pharmacology; D004735:Energy Transfer; D004910:Erythrocyte Membrane / Q000187:drug effects; D005227:Fatty Acids / Q000737:chemistry*; D006461:Hemolysis / Q000187:drug effects; D006538:Heptanoic Acids / Q000737:chemistry; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry; D008074:Lipoproteins / Q000378:metabolism; D054806:Magainins; D008563:Membrane Lipids / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D019308:Palmitic Acid / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D012996:Solutions; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D014357:Trypsin / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism; D014461:Ultracentrifugation; D029867:Xenopus Proteins; D014982:Xenopus laevis
D000935:Antifungal Agents; D023181:Antimicrobial Cationic Peptides; D005227:Fatty Acids; D006538:Heptanoic Acids; D008051:Lipid Bilayers; D008074:Lipoproteins; D054806:Magainins; D008563:Membrane Lipids; D010743:Phospholipids; D012996:Solutions; D029867:Xenopus Proteins; C053301:magainin 2 peptide, Xenopus; C016173:undecanoic acid; D019308:Palmitic Acid; D014364:Tryptophan; D014357:Trypsin; D019286:Endopeptidase K