Dennison, Sarah R., Kim, Young Soo, Cha, Hyung Joon and Phoenix, David A.
Investigations into the ability of the peptide, HAL18, to interact with bacterial membranes.
European Biophysics Journal, 38
Halocidin was isolated from hemocytes, Halocynthia aurantium as a heterodimeric peptide consisting of two α-helical subunits, Hal15 and Hal18. Hal18 was shown to have antibacterial properties against Bacillus subtilis (MLC = 15 μM) and Escherichia coli (MLC = 100 μM). The peptide was shown to produce stable monolayers, which were characteristic of α-helical peptides predicted to orientate parallel to the surface of the interface. Constant area assays showed that Hal18 was surface active (4 μM) inducing surface pressure changes >30 mN m−1 characteristic of membrane interactive peptides. The peptide induced stable surface pressure changes in monolayers that were mimetic of B. subtilis membranes (circa 7 mN m−1) and E. coli membrane-mimics (circa 4 mN m−1). Hal18 inserted readily into zwitterionic DOPE and anionic DOPG monolayers inducing surface pressure changes circa 8 mN m−1 in both cases, providing evidence that interaction is not headgroup specific. Thermodynamic analysis of compression isotherms showed that the presence of Hal18 destabilised B. subtilis membranes (ΔG Mix > 0), which is in contrast to its stabilising effect on E. coli lipid extract implying the differential antimicrobial efficacy may be driven by lipid packing.
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