title: Investigation of ligand-binding sites of the acetylcholine receptor using photoactivatable derivatives of neurotoxin II from Naja naja oxiana.
abstract: Several photoaffinity derivatives of neurotoxin II from the venom of the central Asian cobra Naja naja oxiana have been prepared. After reaction of the 125I-labeled derivatives with the nicotinic acetylcholine receptor from electric organ, the alpha-subunit of the nAChR is almost exclusively labeled by the derivative carrying the photoactivatable group in position Lys46. In contrast to this, a reactive group at Lys26 predominantly labels the gamma- and delta-subunits, while the alpha- and beta-subunits incorporate much less radioactivity. Competition experiments with d-tubocurarine show that the gamma-subunit is labeled when this derivative occupies the high affinity d-tubocurarine-binding site, while the delta-subunit is labeled by the toxin bound at the low-affinity d-tubocurarine site. A model is discussed for the orientation of different loops of the toxin molecules in the binding site for agonists and competitive antagonists.
authors.affiliation: Institut für Biochemie, Freie Universität Berlin, Germany.
authors.forename: H J
authors.initials: HJ
authors.lastname: Kreienkamp
authors.forename: Y N
authors.initials: YN
authors.lastname: Utkin
authors.forename: C
authors.initials: C
authors.lastname: Weise
authors.forename: J
authors.initials: J
authors.lastname: Machold
authors.forename: V I
authors.initials: VI
authors.lastname: Tsetlin
authors.forename: F
authors.initials: F
authors.lastname: Hucho
mesh_terms: D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D002852:Chromatography, Ion Exchange; D003039:Cobra Neurotoxin Proteins; D004546:Elapid Venoms / Q000302:isolation & purification / Q000378:metabolism*; D004557:Electric Organ / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007457:Iodine Radioisotopes; D008024:Ligands; D046911:Macromolecular Substances; D009498:Neurotoxins / Q000302:isolation & purification / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000302:isolation & purification / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014101:Torpedo; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D003039:Cobra Neurotoxin Proteins; D004546:Elapid Venoms; D007457:Iodine Radioisotopes; D008024:Ligands; D046911:Macromolecular Substances; D009498:Neurotoxins; D011978:Receptors, Nicotinic; C076649:neurotoxin II, Naja naja oxiana; D014403:Tubocurarine