Role of phosphatidylglycerols in the stability of bacterial membranes

An extensive 100-ns molecular dynamics simulation of lipid bilayer composed of mixture of phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) was performed to elucidate the role of PGs to the stability of bacterial membranes. In addition, a control simulation of pure PE over 150 ns was performed. We observed that PGs decrease both the PE headgroup protrusions into the water phase, and the PE headgroup motion along bilayer normal. The above effects are caused by stronger inter-lipid interactions in the mixed bilayer: the number of hydrogen bonds created by PEs is 34% higher in the mixed than in the pure bilayer. Another contribution is due to the numerous ion-mediated inter-lipid links, which strongly enhance interface stability. That provides a plausible mechanism for preventing lipid desorption from the membrane, for example, under the influence of an organic solvent. A more compact and less dynamic interface structure also decreases membrane permeability. That provides a possible mechanism for stabilizing, e.g., bacterial membranes.