Halictine-1 (Hal-1) – a linear antibacterial dodecapeptide isolated from the venom of the eusocial bee Halictus sexcinctus – has been subjected to a detailed spectroscopic study including circular dichroism, fluorescence and vibrational spectroscopy. We investigated Hal-1's ability to adopt an amphipathic α-helical structure upon interaction with model lipid based bacterial membranes (phosphatidylcholine/phosphatidylglycerol based large unilamellar vesicles, sodium dodecylsulfate micelles) and helix inducing components (trifluoroethanol). It was found that Hal-1 responds sensitively to composition of the membrane model and to peptide/lipid ratio. Amphipathic nature of the helical Hal-1 seems to favour flat charged surfaces of the model lipid particles over the non-directional interaction with trifluoroethanol. Increasing fraction of polyproline II type conformation was detected at low peptide/lipid ratios.
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