title: Multiple allosteric sites on muscarinic receptors.
abstract: Proteins and small molecules are capable of regulating the agonist binding and function of G-protein coupled receptors by multiple allosteric mechanisms. In the case of muscarinic receptors, there is the well-characterised allosteric site that binds, for example, gallamine and brucine. The protein kinase inhibitor, KT5720, has now been shown to bind to a second allosteric site and to regulate agonist and antagonist binding. The binding of brucine and gallamine does not affect KT5720 binding nor its effects on the dissociation of [3H]-N-methylscopolamine from M1 receptors. Therefore it is possible to have a muscarinic receptor with three small ligands bound simultaneously. A model of the M1 receptor, based on the recently determined structure of rhodopsin, has the residues that have been shown to be important for gallamine binding clustered within and to one side of a cleft in the extracellular face of the receptor. This cleft may represent the access route of acetylcholine to its binding site.
authors.affiliation: Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London, UK. nbirdsa@nimr.mrc.ac.uk
authors.forename: N J
authors.initials: NJ
authors.lastname: Birdsall
authors.forename: S
authors.initials: S
authors.lastname: Lazareno
authors.forename: A
authors.initials: A
authors.lastname: Popham
authors.forename: J
authors.initials: J
authors.lastname: Saldanha
mesh_terms: D000495:Allosteric Site; D002227:Carbazoles; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology; D008024:Ligands; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011758:Pyrroles / Q000737:chemistry / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019311:Staurosporine / Q000737:chemistry / Q000494:pharmacology
chemical_list: D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D008024:Ligands; D011758:Pyrroles; D011976:Receptors, Muscarinic; C057416:KT 5720; D019311:Staurosporine