| Author/Editor | Bonev, Boyan B; Lam, Yuen-Han; Anderluh, Gregor; Watts, Anthony; Norton, Raymond S | |
| Title | Effects of the eukaryotic pore-forming cytolysin equinatoxin II on lipid membranes and the role of sphingomyelin | |
| Type | članek | |
| Source | Biophys J | |
| Vol. and No. | Letnik 84 | |
| Publication year | 2003 | |
| Volume | str. 2382-92 | |
| Language | eng | |
| Abstract | Equinatoxin II (Eqtll), a protein toxin from the sea anemone Actinia equina, readily creates pores in sphingomyelin-containing lipid membranes. The perturbation by Eqtll of model lipid membranes composed of dimyristoylphosphatidycholine and sphingomyelin (10 mol %) was investigated using wideline phosphorus-31 and deuterium NMR. The preferential interaction between Eqtll (0.1 and 0.4 mol %) and the individual bilayer lipids was studied by 3'P magic angle spinning NMR, and toxin-induced changes in bilayer morphology were examined by freeze-fracture electron microscopy. Both NMR and EM showed the formation of an additional lipid phase in sphingomyelin-containing mixed lipid multilamellar suspensions with 0.4 mol % Eqtll. The new toxin-induced phase consisted of small unilamellar vesicles 20-40 nm in diameter. Deuterium NMR showed that the new lipid phase contains both dimyristoylphosphatidycholine and sphingomyelin. Solid-state 3'P NMR showed an increase in spin-lattice and a decrease in spin-spin relaxation times in mixed-lipid model membranes in the presence of Eqtll, consistent with an increase in the intensity of low frequency motions. The ZH and 3'P spectral intensity distributions confirmed a change in lipid mobility and showed the creation of an isotropic lipid phase, which was identified as the small vesicle structures visible by electron microscopy in the Eqtll-lipid suspensions. The toxin appears to enhance slow motions in the membrane lipids and destabilize the membrane. This effect was greatly enhanced in sphingomyelin-containing mixed lipid membranes compared with pure phosphatidylcholine bilayers, suggesting a preferential interaction between the toxin and bilayer sphingomyelin. | |
| Descriptors | CELL MEMBRANE PERMEABILITY CNIDARIAN VENOMS MEMBRANE LIPIDS SPHINGOMYELINS SEA ANEMONES |