Analysis of calcium-induced effects on the conformation of fengycin

A combination of CD, FT-IR, NMR and fluorescence spectroscopic techniques was applied to elucidate the conformation of fengycin, a natural lipopeptide with antifungal and eliciting activities, in a membrane-mimicking environment and to investigate the effect of calcium ions on the conformation.
We mainly observed that fengycin adopts a turn conformation and that the side chain of glutamate residues plays a key role on the stabilization of the peptide ring backbone conformation. More particularly, the binding of calcium ions by the carboxylic moieties has a consequence on the environment of the tyrosine residues. Our data suggest also an arrangement of fengycin molecules into “-sheet like micelles” in a membrane-mimicking environment and the enhancement of this aggregating effect in presence of calcium ions.
The modulation of the fengycin conformation by the environmental conditions may influence its biological properties.