Date Published: January 4, 2017
Publisher: Public Library of Science
Author(s): Wenting Tang, Chuanfen Pu, Man Li, Andreas Hofmann.
Liposomes constructed from Escherichia coli membrane lipids were used as a pseudo-stationary phase in capillary electrophoresis and immobilised liposome chromatography to evaluate the interaction between antibacterial peptide (ABP) Apep10 and bacterial membrane lipids. The peptide mobility decreased as the concentration of liposomes increased, providing evidence for the existence of this interaction. The binding constant between Apep10 and the Escherichia coli membranes lipid liposome was higher than that of Apep10 with a mixed phospholipids liposome at the same temperature. The capillary electrophoresis results indicate that the binding ability of Apep10 with a liposome was dependent on the liposome’s lipid compositions. Thermodynamic analysis by immobilised liposome chromatography indicated that hydrophobic and electrostatic effects contributed to the partitioning of Apep10 in the membrane lipids. The liposomes constructed from bacterial membrane lipid were more suitable as the model membranes used to study dynamic ABP/membrane interactions than those constructed from specific ratios of particular phospholipids, with its more biomimetic phospholipid composition and contents. This study provides an appropriate model for the evaluation of ABP-membrane interactions.
Antibacterial peptides (ABPs) have attracted much attention due to their potential to overcome bacterial resistance and are promising candidates for novel antibiotics , . It is well established that the first stage of ABPs’ action is to combine with the bacterial cell membrane [3–5]. Therefore, knowledge of this interaction is vital to understand their antibacterial mechanism. However, the natural cell membrane has a very short lifespan, which makes it an imperfect candidate for research. To overcome this shortcoming, self-assembled vesicles known as liposomes have been widely used as model membranes, due to the structural similarities between liposomes and the natural cell membrane, both of which are phospholipid bilayers [6–9].
In this study, CE and ILC analyses using liposomes as pseudo-stationary phases were established to explore the binding of antibacterial peptide Apep10 with an E. coli endogenous membrane lipid liposome and a mixed phospholipid liposome. The binding constants of Apep10 with the liposomes prepared from lipids derived from E. coli membrane lipids and mixed phospholipids were calculated and compared. A spontaneous partitioning process containing hydrophobic effect and electrostatic force might contribute to the action of Apep10. Our data suggest that the pseudo-stationary phase constructed from liposome could provide valuable information that would aid in the characterization of the interactions between ABPs and bacterial membrane lipids. Furthermore, the binding constants and capacity factor estimated support the conclusion that the composition of the target membrane is important for the binding action of ABPs.