title: Model of interaction between a cardiotoxin and dimyristoylphosphatidic acid bilayers determined by solid-state 31P NMR spectroscopy.
abstract: The interaction of cardiotoxin IIa, a small basic protein extracted from Naja mossambica mossambica venom, with dimyristoylphosphatidic acid (DMPA) membranes has been investigated by solid-state 31P nuclear magnetic resonance spectroscopy. Both the spectral lineshapes and transverse relaxation time values have been measured as a function of temperature for different lipid-to-protein molar ratios. The results indicate that the interaction of cardiotoxin with DMPA gives rise to the complete disappearance of the bilayer structure at a lipid-to-protein molar ratio of 5:1. However, a coexistence of the lamellar and isotropic phases is observed at higher lipid contents. In addition, the number of phospholipids interacting with cardiotoxin increases from about 5 at room temperature to approximately 15 at temperatures above the phase transition of the pure lipid. The isotropic structure appears to be a hydrophobic complex similar to an inverted micellar phase that can be extracted by a hydrophobic solvent. At a lipid-to-protein molar ratio of 40:1, the isotropic structure disappears at high temperature to give rise to a second anisotropic phase, which is most likely associated with the incorporation of the hydrophobic complex inside the bilayer.
authors.affiliation: Département de Chimie, Université Laval, Québec, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Picard
authors.forename: M
authors.initials: M
authors.lastname: Pézolet
authors.forename: P E
authors.initials: PE
authors.lastname: Bougis
authors.forename: M
authors.initials: M
authors.lastname: Auger
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D000818:Animals; D016880:Anisotropy; D055592:Biophysical Phenomena; D001703:Biophysics; D004179:Cobra Cardiotoxin Proteins / Q000737:chemistry*; D004546:Elapid Venoms / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008956:Models, Chemical; D015394:Molecular Structure; D010758:Phosphorus / Q000737:chemistry
chemical_list: D000814:Aniline Compounds; D004179:Cobra Cardiotoxin Proteins; D004546:Elapid Venoms; D008051:Lipid Bilayers; D008823:Micelles; D010758:Phosphorus; C050795:N,N-dimethyl-4-anisidine