Structural diversity and mode of action on lipid membranes of three lactoferrin candidacidal peptides

The structure and membrane interactions of three antimicrobial peptides from the lactoferrin family were investigated through different techniques. Circular dichroism shows that the peptides adopt a secondary structure in the presence of DMPC/DMPG, and DSC reveals that they all interact with these membranes, albeit differently, whereas only LFchimera has an effect in pure zwitterionic membranes of DMPC. DSC further shows that membrane action is weakest for LFcin17-30, increases for LFampin265-284 and is largest for LFchimera. These differences are clearly reflected in a different structure upon interaction, as revealed by SAX. This technique shows that LFcin17-30 only induces membrane segregation (two lamellar phases are apparent upon cooling from fluid phase), whereas LFampin265-284 induces micellization of the membrane with structure compatible to a micellar cubic phase of space group Pm3n, and LFchimera leads to membrane destruction through the formation of two cubic phases, Pn3m and Im3m. These structural results show a remarkable parallel with the ones obtained previously by freeze fracture microscopy of the effect of these peptides against Candida albicans.