Membrane-Binding Properties of the Antimicrobial Peptide Feleucin
Feleucin is a novel antimicrobial peptide extracted from the skin secretion of the toad (Bombina orientalis). Feleucin, with the sequence FLGLLGSLL, has been shown to possess high antimicrobial activity. Very few studies have been devoted to the interaction between feleucin and model membranes. The objective of this study was to investigate the interaction between feleucin and selected model membranes. The selected model membranes were composed of dipalmitoylphosphocholine (DPPC), dilauroylglycerophosphocholine (DLPC), dipalmitoylglycerophosphoethanolamine (DPPE), Palmitoyloleoylglycerophosphocholine (POPC), sphingomyelin (SPM), dioleoylglycerophosphocholine (DOPC), sphingomyelin (SPM), and cholesterol (CHOL). The specific hypothesis we tested was that significant interactions with feleucin does occur with selected members of the model membranes of various compositions. Special emphasis was given to the effect of saturation, head group, and chain length of the lipid on the interactions involving feleucin. A variety of experimental methods including Fourier Transform Infrared (FTIR), Raman, fluorescence, thermogravimetric analaysis (TGA), differential scanning calorimetry (DSC), and atomic force microscopy (AFM) were used. Infrared data indicated that feleucin adopted a mixture of α-helix, β-sheets, and random coils structures. In the presence of model membrane, the secondary structure of feleucin significantly changed. Interaction of feleucin with model membranes occurred through the carbonyl and phosphate groups of the lipids. Raman data revealed that feleucin interacted with model membranes using the C-N stretching group of the phenylalanine residue. Fluorescence data indicated that DPPE had the strongest interaction with feleucin. A very strong interaction was also found between feleucin and the ternary system DPPC-POPC-CHOL. TGA and DSC data indicated that feleucin-DPPE was the most stable complex. The feleucin-POPC and feleucin-DOPC complexes seemed also to be very stable. Atomic force microscopy data showed that the nature of the substrate mattered. The general trend was that the roughness value of gold was greater than that of mica. This may be due to the hydrophobicity of the surface of mica, which prevented the aggregation process of a cationic peptide from fully taking place. The large value of roughness was recorded with the feleucin-DPPE complex. This study provided new insights into the mechanism of interaction of feleucin with model membranes.
"Membrane-Binding Properties of the Antimicrobial Peptide Feleucin"
ETD Collection for Tennessee State University.