The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel

A ring of aligned glutamate residues named the intermediate ring of charge surrounds the intracellular end of the acetylcholine receptor channel and dominates cation conduction (Imoto et al. 1988). Four of the five subunits in mouse-muscle acetylcholine receptor contribute a glutamate to the ring. T...

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Prif Awduron: Wilson, Gary G., Pascual, Juan M., Brooijmans, Natasja, Murray, Diana, Karlin, Arthur
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Iaith:English
Cyhoeddwyd: The Rockefeller University Press 2000
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Original Article
Mynediad Ar-lein:https://ncbi.nlm.nih.gov/pmc/articles/PMC2217203/
https://ncbi.nlm.nih.gov/pubmed/10653890
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spelling pubmed-22172032008-04-22 The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel Wilson, Gary G. Pascual, Juan M. Brooijmans, Natasja Murray, Diana Karlin, Arthur J Gen Physiol Original Article A ring of aligned glutamate residues named the intermediate ring of charge surrounds the intracellular end of the acetylcholine receptor channel and dominates cation conduction (Imoto et al. 1988). Four of the five subunits in mouse-muscle acetylcholine receptor contribute a glutamate to the ring. These glutamates were mutated to glutamine or lysine, and combinations of mutant and native subunits, yielding net ring charges of −1 to −4, were expressed in Xenopus laevis oocytes. In all complexes, the α subunit contained a Cys substituted for αThr244, three residues away from the ring glutamate αGlu241. The rate constants for the reactions of αThr244Cys with the neutral 2-hydroxyethyl-methanethiosulfonate, the positively charged 2-ammonioethyl-methanethiosulfonate, and the doubly positively charged 2-ammonioethyl-2′-ammonioethanethiosulfonate were determined from the rates of irreversible inhibition of the responses to acetylcholine. The reagents were added in the presence and absence of acetylcholine and at various transmembrane potentials, and the rate constants were extrapolated to zero transmembrane potential. The intrinsic electrostatic potential in the channel in the vicinity of the ring of charge was estimated from the ratios of the rate constants of differently charged reagents. In the acetylcholine-induced open state, this potential was −230 mV with four glutamates in the ring and increased linearly towards 0 mV by +57 mV for each negative charge removed from the ring. Thus, the intrinsic electrostatic potential in the narrow, intracellular end of the open channel is almost entirely due to the intermediate ring of charge and is strongly correlated with alkali-metal-ion conductance through the channel. The intrinsic electrostatic potential in the closed state of the channel was more positive than in the open state at all values of the ring charge. These electrostatic properties were simulated by theoretical calculations based on a simplified model of the channel. The Rockefeller University Press 2000-02-01 /pmc/articles/PMC2217203/ /pubmed/10653890 Text en © 2000 The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
institution US National Library of Medicine
collection PubMed Central
language English
format Article
topic Original Article
spellingShingle Original Article
Wilson, Gary G.
Pascual, Juan M.
Brooijmans, Natasja
Murray, Diana
Karlin, Arthur
The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel
description A ring of aligned glutamate residues named the intermediate ring of charge surrounds the intracellular end of the acetylcholine receptor channel and dominates cation conduction (Imoto et al. 1988). Four of the five subunits in mouse-muscle acetylcholine receptor contribute a glutamate to the ring. These glutamates were mutated to glutamine or lysine, and combinations of mutant and native subunits, yielding net ring charges of −1 to −4, were expressed in Xenopus laevis oocytes. In all complexes, the α subunit contained a Cys substituted for αThr244, three residues away from the ring glutamate αGlu241. The rate constants for the reactions of αThr244Cys with the neutral 2-hydroxyethyl-methanethiosulfonate, the positively charged 2-ammonioethyl-methanethiosulfonate, and the doubly positively charged 2-ammonioethyl-2′-ammonioethanethiosulfonate were determined from the rates of irreversible inhibition of the responses to acetylcholine. The reagents were added in the presence and absence of acetylcholine and at various transmembrane potentials, and the rate constants were extrapolated to zero transmembrane potential. The intrinsic electrostatic potential in the channel in the vicinity of the ring of charge was estimated from the ratios of the rate constants of differently charged reagents. In the acetylcholine-induced open state, this potential was −230 mV with four glutamates in the ring and increased linearly towards 0 mV by +57 mV for each negative charge removed from the ring. Thus, the intrinsic electrostatic potential in the narrow, intracellular end of the open channel is almost entirely due to the intermediate ring of charge and is strongly correlated with alkali-metal-ion conductance through the channel. The intrinsic electrostatic potential in the closed state of the channel was more positive than in the open state at all values of the ring charge. These electrostatic properties were simulated by theoretical calculations based on a simplified model of the channel.
author Wilson, Gary G.
Pascual, Juan M.
Brooijmans, Natasja
Murray, Diana
Karlin, Arthur
author_facet Wilson, Gary G.
Pascual, Juan M.
Brooijmans, Natasja
Murray, Diana
Karlin, Arthur
author_sort Wilson, Gary G.
title The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel
title_short The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel
title_full The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel
title_fullStr The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel
title_full_unstemmed The Intrinsic Electrostatic Potential and the Intermediate Ring of Charge in the Acetylcholine Receptor Channel
title_sort intrinsic electrostatic potential and the intermediate ring of charge in the acetylcholine receptor channel
publisher The Rockefeller University Press
publisher_facet The Rockefeller University Press
publishDate 2000
url https://ncbi.nlm.nih.gov/pmc/articles/PMC2217203/
https://ncbi.nlm.nih.gov/pubmed/10653890
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