The Nicotinic Cholinergic Receptor: Correlation of Molecular Structure with Functional Properties

Conti‐Tronconi, Bianca M.; Raftery, Michael A.

doi:10.1146/annurev.bi.51.070182.002423

Cited by 447 publications

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“…Its functional reincorporation into artificial membranes or liposomes has further demonstrated that this single protein still mediates AcCh-regulated ion translocation and thus comprises the associated ion channel [reviews in Changeux (1981), Popot (1983), and Anholt et al (1983)l. The elementary AcChR "light form" is a heterologous pentameric protein made up of four distinct and strongly associated polypeptide chains a2/3y8 [reviews in Karlin (1980), Changeux (198 l), and Conti-Tronconi & Raftery (1982)l. Covalent (and noncovalent) analogues of AcCh and snake venom a toxins selectively label the a chains, which therefore carry at least part of the AcCh binding sites (two sites per receptor molecule) [references cited in Tzartos & Changeux (1983)l.…”

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confidence: 99%

Rapid kinetics of agonist binding and permeability response analyzed in parallel on acetylcholine receptor rich membranes from Torpedo marmorata

Heidmann¹,

Bernhardt²,

Neumann³

et al. 1983

Biochemistry

113

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Excitable acetylcholine receptor rich membrane fragments from Torpedo marmorata have been used to measure, in parallel, (1) the permeability response to the fluorescent cholinergic agonist Dns-C,-Cho (in the 0.1 pM to' millimolar concentration range) characterized by both the initial rate of Li+ transport and the rate of channel closure using the rapid-mixing quench-flow technique and (2) the kinetics of interaction of Dns-C,-Cho with the acetylcholine receptor sites using the rapid-mixing stopped-flow technique. Analysis of the kinetics of Dns-C6-Cho binding in the millisecond to minute time scale leads to the identification of at least three conformational states of the acetylcholine receptor: a "low-affinity" one (-50 pM) that can be interconverted in A t the neuromuscular junction and at the electromotor synapse, the neurotransmitter acetylcholine (AcCh)' elicits two distinct classes of reactions. Applied as a brief (millisecond) pulse of high concentration (fraction of millimolar), AcCh causes the rapid opening-or "activation"-of transmembrane ion channels selective for cations (Katz, 1966). When maintained for a longer period of time (fraction of a second or minutes), in contact with the postsynaptic membrane, and at a sufficient concentration (approximately micromolar), AcCh initiates a complex time-dependent decrease of the permeability response-or "desensitization". Both classes of reactions have been kinetically analyzed by various electrophysiological techniques [reviews in Adams (1 98 l), Feltz &Trautmann (1982), andNeher et al. (1983)l. The opening of the ion channel by AcCh takes place in the fraction of millisecond to millisecond time scale and in an "all-or-none" manner at the molecular level (Katz & Miledi, 1970; Munchen, FRG (J.B. and E.N.). Received April 7,1983. This work was supported by grants from the Muscular Dystrophy Association of America, the Fondation de France, the CollEge de France, the MinistZre de la Recherche et de l'hdustrie, the Centre National de la Recherche Scientifique, the Institut National de la Santi et de la Recherche MBdicale, and the Commissariat i I'Energie Atomique. We gratefully acknowledge an EMBO short-term stipend (to J.B.) and the support of the Deutsche Forschungsgemeinschaft (Grant 227 to E.N.).

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confidence: 99%

Rapid kinetics of agonist binding and permeability response analyzed in parallel on acetylcholine receptor rich membranes from Torpedo marmorata

Heidmann¹,

Bernhardt²,

Neumann³

et al. 1983

Biochemistry

113

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“…While our fresh membrane fragments prepared in the presence of 4 mM Ca2+ revealed up to twice as many '251-a-bungarotoxin sites in 0.1% nonionic detergent relative to those assayed in the absence of detergent, nonionic %e binding of acetylcholine (AcCh)' (A in equations and schemes) by the acetylcholine receptor (AcChR; R in equations and schemes) is a key reaction in the chemical control of the bioelectric excitation of cholinergic membranes [for monographs, see Nachmansohn (1959) and Katz (1 969)]. The nicotinic AcChR protein of fish electric organs, which regulates the rapid Na+-K+ fluxes through the electroplax membranes, exhibits major conformational variability consistent with its functional properties [for recent reviews, see Karlin (1980), Changeux (1 98 l), Adams (198 l), Conti-Tronconi & Raftery (1982) and Taylor et al (1983)l. Electrophysiological data from frog neuromuscular junctions, which in their electrical-chemical behavior are similar to that of fsh electric organs, suggested that the AcChR channel coexists in at least two conformational states prior to any AcCh binding: an activatable resting state (RJ and an inactivated desensitized state (Rh) with a binding affinity for AcCh that is higher than that 0006-2960/84/0423-4546$01.50/0 detergent treatment of membrane fragments did not result in any change in total available acetylcholine binding sites.…”

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confidence: 99%

Long-lived metastable state and hysteresis in the binding of acetylcholine to Torpedo californica acetylcholine receptor

Chang¹,

Bock²,

Neumann³

1984

Biochemistry

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Studies of the binding of [3H]acetylcholine to receptor-rich membranes of Torpedo californica electric organ under conditions that normally iead to a state of equilibrium did not give rise to equilibrium binding curves. Instead, the acetylcholine receptor was found to develop very long lived metastable states resulting in hysteresis in binding. Under conditions where the concentration of free [3H]acetylcholine is both less than 0.1 NM and smaller or comparable to the total receptor concentration, the degree of binding of acetylcholine depends on the rate, Le., the mode, of increasing the acetylcholine concentration (rapid mixing vs. dialysis). The equilibrium positive cooperativity in high-affinity acetylcholine binding previously inferred from the data is deceiving; the curvature in Scatchard representations is a consequence of long-lived nonequilibrium distributions between high-affinity and lower affinity receptor conformers. By manipulation of the experimental conditions, true equilibrium binding, resulting in a linear Scatchard binding curve, was obtained and yielded the apparent equilibrium constant, K = 5 f 1 nM at 4 OC.The stoichiometry of the high-affinity site associated with this K value was found to be one acetylcholine per receptor monomer ( M , 250 000) when carefully standardized [3H]-acetylcholine analyzed for both radiopurity and acetylcholine concentration was used. While our fresh membrane fragments prepared in the presence of 4 mM Ca2+ revealed up to twice as many '251-a-bungarotoxin sites in 0.1% nonionic detergent relative to those assayed in the absence of detergent, nonionic %e binding of acetylcholine (AcCh)' (A in equations and schemes) by the acetylcholine receptor (AcChR; R in equations and schemes) is a key reaction in the chemical control of the bioelectric excitation of cholinergic membranes [for monographs, see Nachmansohn (1959) and Katz (1 969)]. The nicotinic AcChR protein of fish electric organs, which regulates the rapid Na+-K+ fluxes through the electroplax membranes, exhibits major conformational variability consistent with its functional properties [for recent reviews, see Karlin (1980), Changeux (1 98 l), Adams (198 l), Conti-Tronconi & Raftery (1982) and Taylor et al. (1983)l. Electrophysiological data from frog neuromuscular junctions, which in their electrical-chemical behavior are similar to that of fsh electric organs, suggested that the AcChR channel coexists in at least two conformational states prior to any AcCh binding: an activatable resting state (RJ and an inactivated desensitized state (Rh) with a binding affinity for AcCh that is higher than that 0006-2960/84/0423-4546$01.50/0 detergent treatment of membrane fragments did not result in any change in total available acetylcholine binding sites. Therefore, we favor the interpretation either that the detergent loosens the membrane and exposes a second sterically hindered a-toxin binding site or that it increases its affinity. Our [3H]acetylcholine binding data with solubilized and purified acetylchol...

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“…This was first identified by use of radiolabelled snake toxin a-Bgtx, which binds specifically, quantitatively and irreversibly to acetylcholine receptor of skeletal muscles [3]. a-Bgtx, has been long used for specific identification, quantification and purification of the receptor [27,6]. The AChR binds to figure Fig.…”

Section: Discussionmentioning

confidence: 99%

“…1 M fractions were collected, dialyzed to remove NH 4 OH and then assessed by indirect ELISA(as indicated in purple line) and radioiodinated b-Bgtx binding (as indicated in filled circles) a-Bgtx, a toxin that is used to isolate AChR from crude receptor preparation [10]. The receptor in its monomeric form has a sedimentation coefficient of 9S and has a subunit composition of 40, 50, 60 and 65 kd [6]. Experimental autoimmune MG (EAMG) is also induced by passive transfer of IgG or sera from patients with MG to mice, were run on SDS-P AGE using a stacking gel of 5 % and a resolving gel of 10 %.…”

Section: Discussionmentioning

confidence: 99%

Presynaptic Membrane Receptor in Human Brain

et al. 2012

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Myasthenia gravis (MG) is an autoimmune disease that results from antibody mediated damage of Acetylcholine receptor (AChR) at the neuromuscular junction. The autoimmune character of MG and pathogenic role of AChR antibodies have been established by several workers i.e., the demonstration of anti-AChR antibodies in about 90 % of MG patients. It has been demonstrated that patients with MG also have antibodies against a second protein named presynaptic membrane receptor (PsmR), which is identified by utilizing b-Bgtx, a ligand which binds to PsmR. Using b-Bgtx Sepharose 4B affinity matrix, the PsmR was purified from different regions of human cadaver brain by affinity chromatography. Purified receptor was characterized both by biochemical and immunological procedures. PsmR purified from different regions of the brain shows a specific activity of 0.37 ± 0.01, 0.39 ± 0.02 and 0.43 ± 0.005 nM/ lg of protein in Parietal lobe,

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The Nicotinic Cholinergic Receptor: Correlation of Molecular Structure with Functional Properties

Cited by 447 publications

References 0 publications

Rapid kinetics of agonist binding and permeability response analyzed in parallel on acetylcholine receptor rich membranes from Torpedo marmorata

Rapid kinetics of agonist binding and permeability response analyzed in parallel on acetylcholine receptor rich membranes from Torpedo marmorata

Long-lived metastable state and hysteresis in the binding of acetylcholine to Torpedo californica acetylcholine receptor

Presynaptic Membrane Receptor in Human Brain

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