Ligand efficacy and affinity in an interacting 7TM receptor model.
Quantitative understanding of the activation of G protein-coupled receptors is based mostly on some theoretical models that describe the interaction between ligand and protein partners and the activation process of the receptor. All of these models provide different definitions for observable affinity or efficacy. However, the property common to such parameters defined in the context of these models is that they are always independent of the concentration of the receptor molecule. This is based on the assumption that receptors do not interact with each other appreciably. In this article, experimental evidence for which this assumption does not seem to apply is discussed and an oligomerization model for seven-transmembrane-domain receptors that explains the relationship between receptor concentration, apparent affinity and efficacy is provided.
Ongun Onaran
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Ankara University Faculty of Medicine, Dept Pharmacology and Clinical Pharmacology, Sihhiye 06100, Ankara, Turkey.
Gürdal
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D006801:Humans; D008024:Ligands; D008954:Models, Biological; D019718:Receptors, CXCR4
D008024:Ligands; D019718:Receptors, CXCR4