title: Multiple active receptor conformation, agonist efficacy and maximum effect of the system: the conformation-based operational model of agonism.
abstract: The operational model of agonism assumes that the maximum effect a particular receptor system can achieve (the Em parameter) is fixed. Em estimates are above but close to the asymptotic maximum effects of endogenous agonists. The concept of Em is contradicted by superagonists and those positive allosteric modulators that significantly increase the maximum effect of endogenous agonists. An extension of the operational model is proposed that assumes that the Em parameter does not necessarily have a single value for a receptor system but has multiple values associated to multiple active receptor conformations. The model provides a mechanistic link between active receptor conformation and agonist efficacy, which can be useful for the analysis of agonist response under different receptor scenarios.
authors.affiliation: Laboratory of Systems Pharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Roche
authors.forename: Debora
authors.initials: D
authors.lastname: Gil
authors.forename: Jesús
authors.initials: J
authors.lastname: Giraldo
mesh_terms: D008954:Models, Biological; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000819:agonists* / Q000737:chemistry
chemical_list: D011956:Receptors, Cell Surface