title: Reductive methylation as a probe of the heat-labile alpha-bungarotoxin-acetylcholine receptor membrane complex: evidence for surface interactions.
abstract: alpha-Bungarotoxin (alpha-Bgt) is a potent postsynaptic neurotoxin which blocks neurotransmission by binding very tightly to the acetylcholine-receptor (AcChR) protein. We have previously shown (P. Calvo-Fernandez, and M. Martinez-Carrion (1981) Arch. Biochem. Biophys. 208, 154-159) that alpha-Bgt free in its native solution conformation incorporates 12 methyl groups when reductively methylated using formaldehyde and sodium cyanoborohydride. We now show that when the alpha-Bgt molecule is bound to the AcChR contained in native membranes prepared from Torpedo californica electroplax, the number of accessible methylation sites is significantly reduced. This favors a model of alpha-Bgt-AcChR interaction involving significant numbers of lysyl moieties distributed over a reasonably large surface of the toxin molecule. In addition, this paper presents a novel procedure for the rapid and nondestructive dissociation of the toxin-AcChR membrane complex which takes advantage of the thermal instability of the complex.
mesh_terms: D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004355:Drug Stability; D004557:Electric Organ / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D008745:Methylation; D010084:Oxidation-Reduction; D011950:Receptors, Cholinergic / Q000378:metabolism*; D014101:Torpedo
chemical_list: D002038:Bungarotoxins; D011950:Receptors, Cholinergic