| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Biophysical Sciences, State University of New York at Buffalo 14214, USA.
1. The kinetic properties of cloned mouse embryonic nicotinic acetylcholine receptors (AChRs) expressed in HEK 293 cells or Xenopus oocytes were examined using high concentrations of acetylcholine (ACh), carbamylcholine (CCh), or tetramethylammonium (TMA). The rate constants of agonist binding and channel gating were estimated by fitting kinetic models to idealized open and closed intervals over a range of agonist concentrations. 2. Once doubly liganded, TMA-activated receptors open at approximately 3000 s-1. The equilibrium binding constants for TMA are 525 and 12,800 microM. Doubly liganded CCh-activated receptors open at approximately 11,500 s-1; the equilibrium binding constants for this agonist are 14 and 570 microM. If we assume that doubly liganded, ACh-activated receptors open at 60,000 s-1, then the equilibrium binding constants for ACh are 20 and > 650 microM, similar to those for CCh. For all three agonists the higher affinity site both binds and releases agonists more slowly than does the lower affinity site. 3. ACh and CCh bind to the two sites equally rapidly, at approximately 2 x 10(7) and 4 x 10(7) M-1 s-1 at the first and second binding sites, respectively. Compared with ACh, the TMA association rate is approximately 100 times slower at the first binding site, and approximately 30 times slower at the second binding site. These results indicate that at both binding sites the association rate of TMA is not limited by diffusional or steric factors. 4. All three agonists dissociate from the receptor binding sites at similar rates. The dissociation rate for all agonists was approximately 40 times slower at the first binding site than at the second. These results suggest that the interaction of the quarternary amine moiety with the receptor determines the rate of release of the agonist, and that the nature of this interaction is quite different at the two binding sites. 5. Although the channel opening rates for the three agonists varied approximately 20-fold, the channel closing rates were not strongly agonist dependent, and varied less than 3-fold. We speculate that the ester moiety of the agonist promotes both rapid binding and fast opening of the ligand receptors, and that interactions of the quarternary amine moiety of the agonist with the receptor determine the channel closing rate constant.
This article has been cited by other articles:
|
|
 |
|
  T.-Y. Wu, C. M. Smith, S. M. Sine, and M. M. Levandoski Morantel Allosterically Enhances Channel Gating of Neuronal Nicotinic Acetylcholine {alpha}3{beta}2 Receptors Mol. Pharmacol., August 1, 2008; 74(2): 466 - 475. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Purohit and C. Grosman Estimating Binding Affinities of the Nicotinic Receptor for Low-efficacy Ligands Using Mixtures of Agonists and Two-dimensional Concentration-Response Relationships J. Gen. Physiol., May 30, 2006; 127(6): 719 - 735. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Shelley and D. Colquhoun A human congenital myasthenia-causing mutation ({varepsilon}L78P) of the muscle nicotinic acetylcholine receptor with unusual single channel properties J. Physiol., April 15, 2005; 564(2): 377 - 396. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Y. Lee and S. M. Sine Invariant Aspartic Acid in Muscle Nicotinic Receptor Contributes Selectively to the Kinetics of Agonist Binding J. Gen. Physiol., October 25, 2004; 124(5): 555 - 567. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. S. Dahan, M. I. Dibas, E. J. Petersson, V. C. Auyeung, B. Chanda, F. Bezanilla, D. A. Dougherty, and H. A. Lester A fluorophore attached to nicotinic acetylcholine receptor {beta}M2 detects productive binding of agonist to the {alpha}{delta} site PNAS, July 6, 2004; 101(27): 10195 - 10200. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Auerbach Life at the Top: The Transition State of AChR Gating Sci. Signal., June 24, 2003; 2003(188): re11 - re11. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M. Sine, X.-M. Shen, H.-L. Wang, K. Ohno, W.-Y. Lee, A. Tsujino, J. Brengmann, N. Bren, J. Vajsar, and A. G. Engel Naturally Occurring Mutations at the Acetylcholine Receptor Binding Site Independently Alter ACh Binding and Channel Gating J. Gen. Physiol., September 30, 2002; 120(4): 483 - 496. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. J. Prince, R. A. Pennington, and S. M. Sine Mechanism of Tacrine Block at Adult Human Muscle Nicotinic Acetylcholine Receptors J. Gen. Physiol., August 26, 2002; 120(3): 369 - 393. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Wenningmann and J. P. Dilger The Kinetics of Inhibition of Nicotinic Acetylcholine Receptors by (+)-Tubocurarine and Pancuronium Mol. Pharmacol., October 1, 2001; 60(4): 790 - 796. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Demazumder and J. P. Dilger The Kinetics of Competitive Antagonism by Cisatracurium of Embryonic and Adult Nicotinic Acetylcholine Receptors Mol. Pharmacol., October 1, 2001; 60(4): 797 - 807. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Wenningmann, M. Barann, A. M. Vidal, and J. P. Dilger The Effects of Isoflurane on Acetylcholine Receptor Channels: 3. Effects of Conservative Polar-to-Nonpolar Mutations within the Channel Pore Mol. Pharmacol., September 1, 2001; 60(3): 584 - 594. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. J. Prince and S. M. Sine Acetylcholine and Epibatidine Binding to Muscle Acetylcholine Receptors Distinguish between Concerted and Uncoupled Models J. Biol. Chem., July 9, 1999; 274(28): 19623 - 19629. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Forman and Q. Zhou Novel Modulation of a Nicotinic Receptor Channel Mutant Reveals that the Open State Is Stabilized by Ethanol Mol. Pharmacol., January 1, 1999; 55(1): 102 - 108. [Abstract] [Full Text]
|
|
|
|
 |
|
 M. V. Jones, Y. Sahara, J. A. Dzubay, and G. L. Westbrook Defining Affinity with the GABAA Receptor J. Neurosci., November 1, 1998; 18(21): 8590 - 8604. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Bouzat, A. M. Roccamo, I. Garbus, and F. J. Barrantes Mutations at Lipid-Exposed Residues of the Acetylcholine Receptor Affect Its Gating Kinetics Mol. Pharmacol., July 1, 1998; 54(1): 146 - 153. [Abstract]
|
|
|
|
|
|
R. J. Prince and S. M. Sine Epibatidine Binds with Unique Site and State Selectivity to Muscle Nicotinic Acetylcholine Receptors J. Biol. Chem., April 3, 1998; 273(14): 7843 - 7849. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. R. Kem, V. M. Mahnir, R. L. Papke, and C. J. Lingle Anabaseine Is a Potent Agonist on Muscle and Neuronal Alpha-Bungarotoxin-Sensitive Nicotinic Receptors J. Pharmacol. Exp. Ther., December 1, 1997; 283(3): 979 - 992. [Abstract] [Full Text]
|
|
|
|
|
|
M. Milone, H.-L. Wang, K. Ohno, T. Fukudome, J. N. Pruitt, N. Bren, S. M. Sine, and A. G. Engel Slow-Channel Myasthenic Syndrome Caused By Enhanced Activation, Desensitization, and Agonist Binding Affinity Attributable to Mutation in the M2 Domain of the Acetylcholine Receptor alpha Subunit J. Neurosci., August 1, 1997; 17(15): 5651 - 5665. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. J. Prince and S. M. Sine Molecular Dissection of Subunit Interfaces in the Acetylcholine Receptor. IDENTIFICATION OF RESIDUES THAT DETERMINE AGONIST SELECTIVITY J. Biol. Chem., October 18, 1996; 271(42): 25770 - 25777. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
