The impact of membrane lipid composition on antimicrobial function of an α-helical peptide

VP1, a putative α-helical antimicrobial peptide (α-AMP) inhibited growth of Bacillus subtilis and Escherichia coli at 500 μM. The peptide induced stable surface pressure changes in monolayers formed from B. subtilis native lipid extract (circa 4.5 mN m-1) but transient pressure changes in corresponding E. coli monolayers (circa 1.0 mN m-1), which led to monolayer disintegration. Synthetic lipid monolayers mimetic of the extracts were used to generate compression isotherms. Thermodynamic analysis of B. subtilis isotherms indicated membrane stabilisation by VP1 (ΔGMix 0). Destabilisation correlated with PE levels present and appeared to involve a mechanism resembling those used by tilted peptides. These data emphasise that structure / function analysis of α-AMPs must consider not only their structural characteristics but also the lipid make-up of the target microbial membrane