The protein erylysin A (EryA), isolated from the mushroom Pleurotus eryngii, binds strongly to membranes containing ceramide phosphoethanolamine and cholesterol. Recently, the binding of fluorescently labeled EryA (EryA-EGFP) to cardiolipin, a lipid found in bacterial membranes, mitochondria and chloroplasts, was confirmed. Cardiolipin affects the structure and function of membranes and is involved in the regulation of programmed cell death (apoptosis), where it is transferred from the inner mitochondrial membrane to the outer mitochondrial membrane and from there to the plasmalemma. We analyzed the interaction of EryA with lipid vesicles containing different mole ratios of cardiolipin using the surface plasmon resonance method. We demonstrated a positive correlation between cardiolipin concentration and EryA binding intensity. We also monitored the influence of the molar ratio of cardiolipin on the membrane ordering, where we successfully demonstrated the negative influence of cardiolipin on this parameter using fluorescence anisotropy. Finally, we successfully labeled apoptotic (mammalian) MDCK cells with EryA-mCherry and most likely proved the transport of cardiolipin to the plasmalemma during apoptosis.
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