Curariform Antagonists Bind in Different Orientations to the Nicotinic Receptor Ligand Binding Domain

Wang, Hailong; Bren, Nina; Sine, Steven M.

doi:10.1074/jbc.m304366200

Cited by 27 publications

(41 citation statements)

References 26 publications

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“…quaternary ammonium analog, metocurine, bind in distinctly different orientations in both the AChBP and the muscle nAChR (16,17). Moreover, the prediction of two distinct epibatidine binding orientations in the ␣4␤2 ABS parallels the prediction that dTC and metocurine can bind in distinct orientations in the AChBP and human ␣-⑀ ABS, respectively (16,17).…”

Section: Binding Modes Of [mentioning

confidence: 73%

“…Moreover, the prediction of two distinct epibatidine binding orientations in the ␣4␤2 ABS parallels the prediction that dTC and metocurine can bind in distinct orientations in the AChBP and human ␣-⑀ ABS, respectively (16,17). Our interpretation is based upon a plausible, but unproven, assumption that cleavage of the C-Cl bond of epibatidine produces the only reactive intermediate, and it is also possible that the differences in the patterns of [ 3 H]epibatidine photolabeling between the Torpedo and ␣4␤2 nAChRs result from differences in the structures of the transmitter binding sites between the two nAChRs, including the position and orientations of the core aromatic amino acids.…”

Section: Binding Modes Of [mentioning

confidence: 99%

“…Mutational analyses and molecular docking calculations have also provided evidence that two molecules of very similar structure may actually bind to a single receptor in very different orientations, as seen for two high affinity antagonists, D-tubocurarine and its quaternary ammonium analog metocurine, binding to the AChBP and to the muscle nAChR (16,17).…”

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confidence: 99%

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[3H]Epibatidine Photolabels Non-equivalent Amino Acids in the Agonist Binding Site of Torpedo and α4β2 Nicotinic Acetylcholine Receptors

Srivastava¹,

Hamouda²,

Pandhare³

et al. 2009

Journal of Biological Chemistry

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Nicotinic acetylcholine receptor (nAChR) agonists, such as epibatidine and its molecular derivatives, are potential therapeutic agents for a variety of neurological disorders. In order to identify determinants for subtype-selective agonist binding, it is important to determine whether an agonist binds in a common orientation in different nAChR subtypes. To compare the mode of binding of epibatidine in a muscle and a neuronal nAChR, we photolabeled Torpedo ␣ 2 ␤␥␦ and expressed human ␣4␤2

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Section: Binding Modes Of [mentioning

confidence: 73%

Section: Binding Modes Of [mentioning

confidence: 99%

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[3H]Epibatidine Photolabels Non-equivalent Amino Acids in the Agonist Binding Site of Torpedo and α4β2 Nicotinic Acetylcholine Receptors

Srivastava¹,

Hamouda²,

Pandhare³

et al. 2009

Journal of Biological Chemistry

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“…Although a complete atomic structure has not been determined for any member of the superfamily, atomic resolution data recently emerged for AChBP (3,4), a close homolog of the ligand binding domain of the ␣7 neuronal nicotinic receptor. AChBP has proven to be a valuable model system for clarifying aspects of ligand recognition in nicotinic receptors, including structural modeling (5-7), dynamics of receptor ligand binding domains (8), computational docking of ligands (9,10), and direct monitoring of ligand occupancy by changes in intrinsic Trp fluorescence (11,12).…”

mentioning

confidence: 99%

Agonist-mediated Conformational Changes in Acetylcholine-binding Protein Revealed by Simulation and Intrinsic Tryptophan Fluorescence

Gao

Bren

Burghardt

et al. 2005

Journal of Biological Chemistry

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126

133

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Chemical signaling throughout the organism is initiated by molecular recognition of small biomolecules by receptor binding sites. Recognition is accompanied by conformational changes of the binding site, through induced fit, selection of pre-existing conformers, or a combination of the two, and these are amplified over distance and time to produce the biological response. In the case of rapidly gated synaptic receptors, the amplification propagates within the receptor macromolecule itself and occurs within as little as tens of microseconds (1). Structural counterparts of the initial recognition step likely evolved to provide this close spatial and temporal coupling. To understand the initial recognition step in rapidly gated synaptic receptors, we examined conformational changes due to agonist occupancy in AChBP, 1 a prototype of the nicotinic receptor ligand binding domain (2).The nicotinic receptor belongs to the Cys loop superfamily of rapidly gated synaptic receptors that transduce agonist binding into opening of an intrinsic ion pore. Although a complete atomic structure has not been determined for any member of the superfamily, atomic resolution data recently emerged for AChBP (3, 4), a close homolog of the ligand binding domain of the ␣7 neuronal nicotinic receptor. AChBP has proven to be a valuable model system for clarifying aspects of ligand recognition in nicotinic receptors, including structural modeling (5-7), dynamics of receptor ligand binding domains (8), computational docking of ligands (9, 10), and direct monitoring of ligand occupancy by changes in intrinsic Trp fluorescence (11, 12).Here we delineated ACh-dependent conformational changes in AChBP by prolonged MD simulation and compared these with conformational changes detected by steady-state and time-resolved measurements of intrinsic Trp fluorescence. MD simulation revealed asymmetric relaxation of the AChBP homopentamer without ACh bound, but maintenance of the symmetrical structure with ACh bound. Differences between the ACh-free and ACh-bound structures revealed conformational changes linked to agonist occupancy. Conformational changes predicted by simulation were verified by measurements of intrinsic Trp fluorescence, showing that binding of ACh establishes close register of two Trp side chains from opposing subunits and draws the peripheral C-loop inward to occlude the entrance of the binding cavity. EXPERIMENTAL PROCEDURESMolecular Docking and Dynamics Simulation-We used the AMBER 7 program (13) to conduct molecular dynamics (MD) simulation of AChBP in the presence of explicit solvent molecules at room temperature, without ACh bound or with ACh bound to one, two, or all five binding sites. Atomic coordinates of AChBP (3) were downloaded from the Protein Data Bank (Protein Data Bank code 1I9B). To prepare the protein structure for docking and MD simulation, water, ions, and HEPES were first removed from the crystal structure. Partial atomic charges were then assigned to each atom of the protein using the restrained electrostatic poten...

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“…Recent studies about how nicotinic ligands bind to muscle-type nAChRs have been based on curare derivatives, nicotine, epibatidine, choline derivatives, and trimethylammonium (192,189). Descriptions of ligand-nAChR interactions might need to consider differences arising from seemingly minor changes in ligand structure and in subtype and species of nAChRs.…”

Section: Muscle Nachrsmentioning

confidence: 99%

Structural answers and persistent questions about how nicotinic receptors work

Wells¹

2008

Front Biosci

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The electron diffraction structure of nicotinic acetylcholine receptor (nAChR) from Torpedo marmorata and the X-ray crystallographic structure of acetylcholine binding protein (AChBP) are providing new answers to persistent questions about how nAChRs function as biophysical machines and as participants in cellular and systems physiology. New high-resolution information about nAChR structures might come from advances in crystallography and NMR, from extracellular domain nAChRs as high fidelity models, and from prokaryotic nicotinoid proteins. At the level of biophysics, structures of different nAChRs with different pharmacological profiles and kinetics will help describe how agonists and antagonists bind to orthosteric binding sites, how allosteric modulators affect function by binding outside these sites, how nAChRs control ion flow, and how large cytoplasmic domains affect function. At the level of cellular and systems physiology, structures of nAChRs will help characterize interactions with other cellular components, including lipids and trafficking and signaling proteins, and contribute to understanding the roles of nAChRs in addiction, neurodegeneration, and mental illness. Understanding nAChRs at an atomic level will be important for designing interventions for these pathologies. KeywordsAcetylcholine; Addiction; Neurodegeneration; Nicotine; Protein Design; Protein Folding; Protein Structure; Cys-Loop Receptors; Review INTRODUCTIONNicotinic acetylcholine receptors (nAChRs) are integral-membrane, neurotransmitteractivated ion channels in the central and peripheral nervous systems that participate in signal transmission associated with the physiological release of acetylcholine (1). As cationselective ion channels, they depolarize transmembrane voltage when they transition from the closed resting state to the open cation-conducting state by binding agonist. Continued exposure to agonist causes transition from the open state to the closed desensitized state. More than four decades of research have answered many structural questions about nAChRs. Reviews published across these decades reveal the progression of questions and answers (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). Current understanding of the structural basis of how nAChRs work is relatively advanced compared to other areas of ion channel biophysics (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). Despite this level of understanding, however, questions persist, not only about biophysical properties but also about the structural basis of how nAChRs affect cellular and systems physiology (28). NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptBy reviewing research literature published primarily between 2003 and mid-2007, the goals of this review are to describe the current state of understanding of the structures of nAChRs and to describe questions for which atomic-level structural answers still await. WHICH STRUCTURAL FEATURES DEFINE NACHRS AND OTHER CYS-LOOP RECEPTORS?Mammalian genomes contain 16 nAChR subunits ...

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Curariform Antagonists Bind in Different Orientations to the Nicotinic Receptor Ligand Binding Domain

Cited by 27 publications

References 26 publications

[3H]Epibatidine Photolabels Non-equivalent Amino Acids in the Agonist Binding Site of Torpedo and α4β2 Nicotinic Acetylcholine Receptors

[3H]Epibatidine Photolabels Non-equivalent Amino Acids in the Agonist Binding Site of Torpedo and α4β2 Nicotinic Acetylcholine Receptors

Agonist-mediated Conformational Changes in Acetylcholine-binding Protein Revealed by Simulation and Intrinsic Tryptophan Fluorescence

Structural answers and persistent questions about how nicotinic receptors work

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