How does elicitor and antimicrobial fengycin interact with plasma membranes of sensitive cells ?

Fengycin is characterized by its strong antifungal and low hemolytic activities. It has also been recently demonstrated that it has plant elicitor properties and is also able to enhance the elicitors’ activity of surfactin. The cell target of its biological activities is supposed to be plasma membrane. In spite of these interesting biological activities, fengycin has not been extensively investigated probably because of the difficulties related to its production.
In a first time; we have characterized the interfacial properties of fengycin by tensiometry measurements and demonstrated that this surface activity was pH-dependent. In a second time; we have investigated the interactions of the lipopeptide with membrane lipids using model membranes such as Langmuir monolayers and multilammelar vesicles (MLVs). Our results indicate that the lipopeptide was able to penetrate into different lipid monolayers showing a preference for sterol-containing monolayers. In order to better understand the mechanism of the interactions of fengycin with membranes at the molecular level, MLVs with or without fengycin have been analyzed by spectroscopic techniques. We have shown that conformational changes of the lipopeptide occurred in the presence of lipids and they were more significant in the presence of sterol. Moreover, tyrosine residues of the lipopeptide seem to play an important role in these interactions.
In conclusion, we have determined that the surface-active behavior as well as the conformation of fengycin depends on its environment. We have also showed that the lipopeptide does not interact with all class of lipids in the same way and presents a preference for sterols. The presence of key groups within peptide cycle has also been supposed for the biological activities of the lipopeptide.