Alpha-bungarotoxin binding to acetylcholine receptor membranes studied by low angle X-ray diffraction.
The nicotinic acetylcholine receptor (nAChR) carries two binding sites for snake venom neurotoxins. alpha-Bungarotoxin from the Southeast Asian banded krait, Bungarus multicinctus, is a long neurotoxin which competitively blocks the nAChR at the acetylcholine binding sites in a relatively irreversible manner. Low angle x-ray diffraction was used to generate electron density profile structures at 14-A resolution for Torpedo californica nAChR membranes in the absence and presence of alpha-bungarotoxin. Analysis of the lamellar diffraction data indicated a 452-A lattice spacing between stacked nAChR membrane pairs. In the presence of alpha-bungarotoxin, the quality of the diffraction data and the lamellar lattice spacing were unchanged. In the plane of the membrane, the nAChRs packed together with a nearest neighbor distance of 80 A, and this distance increased to 85 A in the presence of toxin. Electron density profile structures were calculated in the absence and presence of alpha-bungarotoxin, revealing a location for the toxin binding sites. In native, fully-hydrated nAChR membranes, alpha-bungarotoxin binds to the nAChR outer vestibule and contacts the surface of the membrane bilayer.
Young
Howard S
HS
Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7. hyoung@biochem.ualberta.ca
Herbette
Leo G
LG
Skita
Victor
V
D000818:Animals; D001665:Binding Sites; D002038:Bungarotoxins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology*; D003198:Computer Simulation; D008954:Models, Biological; D011485:Protein Binding; D011978:Receptors, Nicotinic / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D014101:Torpedo / Q000033:anatomy & histology / Q000502:physiology*; D014961:X-Ray Diffraction / Q000379:methods*; D064569:alpha7 Nicotinic Acetylcholine Receptor
D002038:Bungarotoxins; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor