Interaction of modified neurotoxins fromNaja nigricolliswith the nicotinic acetylcholine receptor fromTorpedo marmorataA Raman spectroscopy study

Abstract

Two derivatives of α-toxin fromNaja nigricollis venom were used in order to study, by resonance Raman spectroscopy, its interaction with the nicotinic acetylcholine (AcCho) receptor from membranes ofTorpedo marmorata electrocytes. The two modified toxins carry either an NO2 group bound to Tyr25 or a nitrophenylthioether (NPS) bound to Trp25. The comparison of the spectra of the free and bound derivatized toxins indicates that the environment of Tyr25 is not perturbed upon binding to the AcCho receptor, but the surroundings of NPS bound to Trp29 are changed. This result indicates that Tyr25 is not involved in binding, while Trp29 of the α-toxin may be in contact with the AcCho receptor. Examination of the spectrum of the AcCho receptor membrane after binding of the NPS-Trp toxin discloses some modifications of the vibrations of the tryptophan and cysteine disulfide bridge of the receptor. These residues are possibly involved in toxin binding