Open AccessInteraction of the P‐type cardiotoxin with phospholipid membranes
Author(s) -
Dubovskii Peter V.,
Lesovoy Dmitry M.,
Dubinnyi Maxim A.,
Utkin Yuri N.,
Arseniev Alexander S.
Publication year - 2003
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2003.03580.x
Subject(s) - cardiotoxin , membrane , phospholipid , chemistry , bilayer , vesicle , lipid bilayer , biophysics , nuclear magnetic resonance spectroscopy , crystallography , stereochemistry , biochemistry , venom , biology
The cardiotoxin (cytotoxin II, or CTII) isolated from cobra snake ( Naja oxiana ) venom is a 60‐residue basic membrane‐active protein featuring three‐finger beta sheet fold. To assess possible modes of CTII/membrane interaction 31 P‐ and 1 H‐NMR spectroscopy was used to study binding of the toxin and its effect onto multilamellar vesicles (MLV) composed of either zwitterionic or anionic phospholipid, dipalmitoylglycerophosphocholine (Pam 2 Gro‐ P Cho) or dipalmitoylglycerophosphoglycerol (Pam 2 Gro‐ P Gro), respectively. The analysis of 1 H‐NMR linewidths of the toxin and 31 P‐NMR spectral lineshapes of the phospholipid as a function of temperature, lipid‐to‐protein ratios, and pH values showed that at least three distinct modes of CTII interaction with membranes exist: (a) nonpenetrating mode; in the gel state of the negatively charged MLV the toxin is bound to the surface electrostatically; the binding to Pam 2 Gro‐ P Cho membranes was not observed; (b) penetrating mode; hydrophobic interactions develop due to penetration of the toxin into Pam 2 Gro‐ P Gro membranes in the liquid‐crystalline state; it is presumed that in this mode CTII is located at the membrane/water interface deepening the side‐chains of hydrophobic residues at the tips of the loops 1–3 down to the boundary between the glycerol and acyl regions of the bilayer; (c) the penetrating mode gives way to isotropic phase, stoichiometrically well‐defined CTII/phospholipid complexes at CTII/lipid ratio exceeding a threshold value which was found to depend at physiological pH values upon ionization of the imidazole ring of His31. Biological implications of the observed modes of the toxin–membrane interactions are discussed.