Source:http://linkedlifedata.com/resource/pubmed/id/12815157
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
1
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pubmed:dateCreated |
2003-6-19
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pubmed:abstractText |
Two epitopes have been identified recently to be responsible for the high-affinity binding of alkane-bisammonium and caracurine V type allosteric ligands to N-methylscopolamine (NMS)-occupied M2 muscarinic acetylcholine receptors, relative to M5 receptors: the amino acid M2-Thr423 at the top of transmembrane region (TM) 7 and an epitope comprising the second extracellular loop (o2) of the M2 receptor including the flanking regions of TM4 and TM5. We aimed to find out whether a single amino acid could account for the contribution of this epitope to binding affinity. Allosteric interactions were investigated in wild-type and mutant receptors in which the orthosteric binding site was occupied by [3H]NMS (5 mM Na,K,Pi buffer, pH 7.4, 23 degrees C). Using M2/M5 chimeric and point-mutated receptors, the relevant epitope was narrowed down to M2-Tyr177. A double point-mutated M2 receptor in which both M2-Tyr177 and M2-Thr423 were replaced by the corresponding amino acids of M5 revealed that these two amino acids account entirely for the (approximately 100-fold) M2/M5 selectivity of the alkane-bisammonium and the caracurine V type allosteric ligands. At NMS-free M2 receptors, the caracurine V derivative also displayed approximately 100-fold M2/M5 selectivity, but the double point mutation reduced the M2 affinity by only approximately 10-fold; thus, additional epitopes may influence selectivity for the free receptors. A three-dimensional model of the M2 receptor was used to simulate allosteric agent docking to NMS-occupied receptors. M2-Tyr177 and M2-Thr423 seem to be located near the junction of the allosteric and the orthosteric areas of the M2 receptor ligand binding cavity.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Amino Acids,
http://linkedlifedata.com/resource/pubmed/chemical/Ligands,
http://linkedlifedata.com/resource/pubmed/chemical/N-Methylscopolamine,
http://linkedlifedata.com/resource/pubmed/chemical/Parasympatholytics,
http://linkedlifedata.com/resource/pubmed/chemical/Receptor, Muscarinic M2,
http://linkedlifedata.com/resource/pubmed/chemical/Receptors, Muscarinic
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pubmed:status |
MEDLINE
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pubmed:month |
Jul
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pubmed:issn |
0026-895X
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
64
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
21-31
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:12815157-Allosteric Regulation,
pubmed-meshheading:12815157-Allosteric Site,
pubmed-meshheading:12815157-Amino Acids,
pubmed-meshheading:12815157-Animals,
pubmed-meshheading:12815157-COS Cells,
pubmed-meshheading:12815157-Humans,
pubmed-meshheading:12815157-Ligands,
pubmed-meshheading:12815157-Models, Molecular,
pubmed-meshheading:12815157-Mutagenesis, Site-Directed,
pubmed-meshheading:12815157-N-Methylscopolamine,
pubmed-meshheading:12815157-Parasympatholytics,
pubmed-meshheading:12815157-Receptor, Muscarinic M2,
pubmed-meshheading:12815157-Receptors, Muscarinic
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pubmed:year |
2003
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pubmed:articleTitle |
Allosteric site on muscarinic acetylcholine receptors: identification of two amino acids in the muscarinic M2 receptor that account entirely for the M2/M5 subtype selectivities of some structurally diverse allosteric ligands in N-methylscopolamine-occupied receptors.
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pubmed:affiliation |
Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Bonn, 53121 Bonn, Germany.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
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