A Spectroscopic Study of the Aggregation State of the Human Antimicrobial Peptide LL-37 in Bacterial versus Host Cell Model Membranes.
The LL-37 antimicrobial peptide is the only cathelicidin peptide found in humans that has antimicrobial and immunomodulatory properties. Because it exerts also chemotactic and angiogenetic activity, LL-37 is involved in promoting wound healing, reducing inflammation, and strengthening the host immune response. The key to the effectiveness of antimicrobial peptides (AMPs) lies in the different compositions of bacterial versus host cell membranes. In this context, antimicrobial peptide LL-37 and two variants were studied in the presence of model membranes with different lipid compositions and charges. The investigation was performed using an experimental strategy that combines the site-directed spin labeling-electron paramagnetic resonance technique with circular dichroism and fluorescence emission spectroscopies. LL-37 interacts with negatively charged membranes forming a stable aggregate, which can likely produce toroidal pores until the amount of bound peptide exceeds a critical concentration. At the same time, we have clearly detected an aggregate with a higher oligomeric degree for interaction of LL-37 with neutral membranes. These data confirm the absence of cell selectivity of the peptide and a more complex role in stimulating host cells.
Department of Biotechnology, Chemistry and Pharmacy, University of Siena , 53100 Siena, Italy.
Alessio
A
Bonucci
Department of Biotechnology, Chemistry and Pharmacy, University of Siena , 53100 Siena, Italy.
Elena
E
Caldaroni
School of Biosciences and Veterinary Medicine, University of Camerino , 62032 Camerino, Italy.
Enrico
E
Balducci
Department of Biotechnology, Chemistry and Pharmacy, University of Siena , 53100 Siena, Italy.
Rebecca
R
Pogni
D019943:Amino Acid Substitution; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000235:genetics; D001419:Bacteria / Q000737:chemistry* / Q000648:ultrastructure; D002462:Cell Membrane / Q000737:chemistry*; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D005057:Eukaryotic Cells / Q000737:chemistry* / Q000648:ultrastructure; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D008567:Membranes, Artificial; D008958:Models, Molecular; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry; D013045:Species Specificity; D013050:Spectrometry, Fluorescence; D054804:Cathelicidins
D023181:Antimicrobial Cationic Peptides; D008081:Liposomes; D008563:Membrane Lipids; D008565:Membrane Proteins; D008567:Membranes, Artificial; D020033:Protein Isoforms; D054804:Cathelicidins