title: Penetration of a cardiotoxin into cardiolipin model membranes and its implications on lipid organization.
abstract: The interaction of cardiotoxin II of Naja mossambica mossambica with cardiolipin model membranes was investigated by binding, fluorescence, resonance energy transfer, fluorescence quenching, 31P NMR, freeze-fracture, and small-angle X-ray experiments. An initially electrostatic binding appeared to be accompanied by a deep penetration, most likely into the acyl chain region of the phospholipids, indicating a hydrophobic contribution to the strong interaction (KD congruent to 5 X 10(-8) M). This binding results in a fusion of unilamellar vesicles as indicated by a fluorescence-based fusion assay, freeze-fracture, and X-ray diffraction. In these fused structures freeze-fracture electron microscopy reveals the appearance of particles, which is accompanied by the induction of an isotropic component in 31P NMR. The well-defined particles are interpreted as inverted micelles, and the localization of the cardiotoxin molecule in these structures is discussed.
mesh_terms: D000818:Animals; D002308:Cardiolipins / Q000302:isolation & purification; D002417:Cattle; D004179:Cobra Cardiotoxin Proteins; D004546:Elapid Venoms; D005614:Freeze Fracturing; D007700:Kinetics; D008081:Liposomes; D008854:Microscopy, Electron; D008954:Models, Biological; D009206:Myocardium; D013050:Spectrometry, Fluorescence; D014961:X-Ray Diffraction
chemical_list: D002308:Cardiolipins; D004179:Cobra Cardiotoxin Proteins; D004546:Elapid Venoms; D008081:Liposomes