The increase in positively charged residues in cecropin D-like Galleria mellonella favors its interaction with membrane models that imitate bacterial membranes

A comparative study of three synthetic peptides, namely neutral Cecropin D-like G. mellonella (WT) and two cationic peptides derived from its sequence, Delta M1 (+5) and Delta M2 (+9) is reported in this work. The influence of charge on the interactions between peptides and membranes and its effect on phase were studied by calorimetric assays. Differential scanning calorimetry (DSC) showed that Delta M2 peptide showed the strongest effect when the membrane contained phosphatidylcholine (PC) and phosphatidylglycerol (PG), increasing membrane fluidization. Fourier transform infrared spectroscopy (FTIR) was used to determine lipid segregation in the presence of peptides. When WT and Delta M1 bound to model membrane containing PG and PC (1:1 molar ratio) a separation of both lipids was observed. Meanwhile, Delta M2 peptide also induced a demixing of PG-peptide rich domains separated from PC. FTIR experiments also suggested that the presence of Delta M1 and Delta M2 peptides increased lipid carbonyl group hydration in DMPG membrane fluid phase, However, hydration at the interface level in fluid phase was notably increased in the presence of WT and Delta M1 peptides in DMPC/DMPG. Overall the increase in positively charged residues favors the interaction of the peptides with the negatively charged membrane and its perturbation. (C) 2017 Elsevier Inc. All rights reserved.