Gil and GoA differentially determine kinetic efficacies of agonists for κ-opioid receptor

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 G alpha(i1)beta(1)gamma(2) or KOR plus G alpha(oA)beta(1)gamma(2), there mas no significant difference between both preparations in the K-i values of various tc-opioid ligands for the displacement of [H-3]U69593 binding. However, a marked difference in the rank order of agonists to stimulate [S-35]GTP gamma S 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. (C) 2000 Federation of European Biochemical Societies.