Towards the Crystal Structure Determination of Muscarinic Acetylcholine Receptors
G protein-coupled receptors (GPCRs) constitute the largest family of receptors encoded by the human genome. Activation and inhibition of GPCRs under the physiological and pathophysiological conditions is largely mediated by chemical ligands (agonists and antagonists) that bind to the orthosteric binding pocket. Orthosteric ligands are, however, often nonspecific, binding to more than one GPCR subtype. In contrast to orthosteric agonists and antagonists, allosteric ligands do not directly compete with hormones and neurotransmitters for binding to the orthosteric binding pocket. Furthermore, allosteric ligands typically occupy structurally diverse regions of receptors and therefore are more selective for specific GPCRs, regulating receptor function in the more subtle ways by either enhancing or diminishing responses to natural ligands such as hormones or neurotransmitters. Recent X-ray crystallographic studies have provided detailed structural information regarding the nature of the orthosteric muscarinic binding site and an outer receptor cavity that can bind allosteric drugs. These new findings may guide the development of selective muscarinic receptor. The procedures involved in the production, purification, and crystallization of GPCRs are introduced here and facilitate a greater understanding of the structural basis of GPCR function.
Key wordsG-protein coupled receptor X-ray crystal structure analysis Muscarinic acetylcholine receptor Antagonist Agonist Orthosteric binding site Allosteric binding site
This work was supported by the Exploratory Research for Advanced Technology (ERATO) program of the Japan Science and Technology Agency (JST) (to T.K.), by the Toray Science Foundation (to T.K.), by Takeda Science Foundation (to T.K., R.S., and H.A.), by Ichiro Kanehara Foundation (to T.K.), by The Sumitomo Foundation (to T.K.), by the Core Research for Evolutional Science and Technology (CREST) program of the JST (to T.K.), and by the Platform for Drug Discovery, Informatics, and Structural Life Science from the Ministry of Education, Culture, Sports, Science and Technology, Japan (to T.K.).
- 7.Bonner TI (1989) New subtypes of muscarinic acetylcholine receptors. Trends Pharmacol Sci Suppl 11:5Google Scholar
- 23.Weiss HM, Haase W, Michel H et al (1998) Comparative biochemical and pharmacological characterization of the mouse 5HT5A 5-hydroxytryptamine receptor and the human beta2-adrenergic receptor produced in the methylotrophic yeast Pichia pastoris. Biochem J 330(Pt 3):1137–1147PubMedCentralPubMedGoogle Scholar