title: Conjugation of a magainin analogue with lipophilic acids controls hydrophobicity, solution assembly, and cell selectivity.
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.
authors.affiliation: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100 Israel.
authors.forename: Dorit
authors.initials: D
authors.lastname: Avrahami
authors.forename: Yechiel
authors.initials: Y
authors.lastname: Shai
mesh_terms: 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
chemical_list: 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