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Updated: Jul 7, 2026

Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
G(i1) and G(oA) differentially determine kinetic efficacies of agonists for kappa-opioid receptor
M Kohno1, N Fukushima, A Yoshida
1Department of Molecular Pharmacology and Neuroscience, Nagasaki University School of Pharmaceutical Sciences, 1-14 Bunkyo-machi, Nagasaki, Japan.
Abstract:
We examined the diversity of single receptor function by measuring receptor-G protein coupling in the baculovirus-Sf21 expression system. In comparative studies using Sf21 cell membranes expressing kappa-opioid receptor (KOR) plus Galpha(i1)beta(1)gamma(2) or KOR plus Galpha(oA)beta(1)gamma(2), there was no significant difference between both preparations in the K(i) values of various kappa-opioid ligands for the displacement of [(3)H]U69593 binding. However, a marked difference in the rank order of agonists to stimulate [(35)S]GTPgammaS binding was observed between both preparations. These findings suggest that agonist efficacy is dependent on the population of different G proteins expressed in various tissues.
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