Leucrocin is a cationic antimicrobial peptide that is found in the white blood cells of crocodiles (Crocodylus siamensis). The amino acid sequence of Leucrocin is NGVQPKY and has a broad range of antimicrobial activity against Gram-positive and Gram-negative bacteria, including Staphylococcus epidermidis, Salmonella typhi and Vibrio cholerae. Very few studies have been conducted to examine the interaction between Leucrocin and model membranes. This project is an investigation of the structural properties of Leucrocin in the solvents SDS (Sodium dodecyl sulfate) and TFE (tri-fluroethanol), as well as the neutral vesicle DPPC (1,2 di-palmitoyl-sn-glycero-3 phosphocholine) and the negatively-charged POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol) using Infrared, fluorescence, NMR and DSC techniques. FTIR spectra indicate that leucrocin adopts a mixture of α-helix and β-sheet structures in the absence of model membranes. A significant increase in α-helix and β-sheet structure content of leucrocin is observed in the presence of TFE and SDS, respectively. In DPPC, the secondary structure of Leucrocin was a mixture of both turn and β-sheet structure, while in POPG it was shown to be mainly turns. Interaction of leucrocin with model membranes was examined using tyrosine fluorescence. Upon addition of the model membranes, the initial fluorescence of leucrocin is quenched. The decrease in fluorescence emission is stronger for SDS and POPG than for TFE and DPPC. Proton NMR spectra suggest the involvment of the N atom of the amide group of leucrocin. DSC technique revealed that leucrocin alters the stability of the phospholipid bilayers

Interaction between the antimicrobial peptide Leucrocin and model membranes

249th National Meeting (2015)

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