Isolation of the nicotinic acetylcholine receptor by biospecific chromatography on insolubilized Naja naja neurotoxin

Conformational properties of the acetylcholine receptor as revealed by studies with constrained depolarizing ligands

“…This is particularly true for trans-3,3'-bisQ and, indeed, it is this constraint that is likely to be responsible for its high activity-i.e., its geometry is closely similar to that of the binding site of AcChoR in its active, depolarized state which, presumably, it stabilizes. Our findings also do not agree with the suggestion of Pauling and Petcher that in the "resting state" the sites on the quaternary groups are about 11 A apart and that they move closer together upon depolarization. The high activity of trans-3,3-bisQ would suggest that the N+-N+ distance is about 11 (24), the nitrogen of the quaternary group of acetylcholine is nearly neutral.…”

“…Our findings also do not agree with the suggestion of Pauling and Petcher that in the "resting state" the sites on the quaternary groups are about 11 A apart and that they move closer together upon depolarization. The high activity of trans-3,3-bisQ would suggest that the N+-N+ distance is about 11 (24), the nitrogen of the quaternary group of acetylcholine is nearly neutral. Seventy percent of the positive charge is distributed among the methyl groups, forming a spherical field of positive electricity.…”

“…Implicit in all of these studies is the existence of a protein-containing receptor that, when bound to a suitable ligand, regulates the permeability of and, hence, the electrical potential across an electrogenic membrane (6). A number of laboratories have reported successful isolation of the AcChoR protein (7)(8)(9)(10)(11)(12) and have examined its properties both when free and when incorporated into membranes.…”

Regulation of Acetylcholine Receptors in Relation to Acetylcholinesterase in Neuroblastoma Cells

“…Affinity-labeling procedures have indicated that there are similarities and differences between the active sites of the receptor and the enzyme (3)(4)(5). Acetylcholinesterase has been purified (6,7), and purified acetylcholine receptors are reported to have no acetylcholinesterase activity (8)(9)(10)(11). The receptor and the enzyme, both of which have sites specific for acetylcholine, may therefore be on different molecules, or there may be different sites on the same molecule that can be experimentally separated (2).…”

Presynaptic and postsynaptic effects of the venom of the Australian tiger snake at the neuromuscular junction

“…All the toxic crude venoms and neurotoxins which have been tested block neuromuscular transmission, generally by binding with postsynaptic receptors so that acetylcholine is less effective in depolarizing the postsynaptic cell. This property of snake venoms has been exploited to investigate and isolate acetylcholine receptors (Barnard, Wieckowski & Chiu, 1971 ;Miledi, Molinoff & Potter, 1971 ;Raftery, Schmidt, Clark & Wolcott, 1971 ;Berg, Kelly, Sargent, Williamson & Hall, 1972;Bosmann, 1972;Franklin & Potter, 1972;Karlsson, Heilbronn & Widlund, 1972;Meunier, Olsen, Menez, Fromageot, Boquet & Changeux, 1972;Raftery, Schmidt & Clark, 1972;. Only the venom from the krait, Bungarus multicinctus, has been found to contain a fraction (/3-bungarotoxin) which acts on nerve terminals rather than on postsynaptic receptors (Lee & Chang, 1966).…”