Ostreolysin A6 (OlyA6), from the mushroom Pleurotus ostreatus, is a 15 kDa protein that specifically senses sphingolipid membrane receptors. In combination with a larger protein pleurotolysin B (PlyB), it assembles into complexes which form transmembrane pores. The membrane binding of OlyA6 can be decreased or prevented by the addition of mono- or di-unsaturated phosphatidylcholine, by replacing cholesterol with other natural sterols or cholesterol derivatives, or by the addition of micromolar concentrations of fatty acids or lysophospholipids such as lysophosphatidylcholine (LPC). High concentrations of LPC act as natural detergents that lyse the membrane, while lower concentractions prevent the formation of OlyA6/PlyB membrane pores. In this Master's thesis, we investigated the influence of LPC on the interaction of OlyA6 with artificial lipid membranes containing sphingolipid receptors, or a glycerophospholipid cardiolipin. Using the fluorescence scattering method, we showed that the addition of LPC affects the ordering of lipid membrane phase. Anisotropy and polarization measurements confirmed that the increased temperature and the addition of LPC slightly reduce the membrane order parameter. Using the calcein release test, we showed that the addition of LPC inhibits the binding and pore-forming activity of OlyA6/PlyB complexes, as it reduces the number of sphingolipid/chlesterol OlyA6 binding sites. We also monitored the interaction of OlyA6 with artificially prepared lipid vesicles and found that the amount of bound OlyA6 depends on the concentration of LPC added.
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