Solubilisation and binding characteristics of a recombinant β 2-adrenergic receptor expressed in the membrane of Escherichia coli for the multianalyte detection of β-agonists and antagonists residues in food-producing animals

Abstract

The number of substances with β-agonistic activity, illegally introduced in meat production or in sports doping as anabolic or β-blocking agents is increasing. Analytical methods suited for their multianalyte detection are thus necessary. In this perspective, receptor assays were developed. The research activities undertaken in this study describe the solubilisation of a recombinant human β 2-adrenergic receptor produced in the inner membrane of genetically modified Escherichia coli, using the detergent n-dodecyl-β- d-maltoside. Its potential to detect the presence of β-agonists or β-blockers in biological samples was evaluated. The solubilised β 2-adrenergic receptor retained its binding affinity in a radio-receptor assay based on the competition for the binding to receptors between a ligand (β-agonist or antagonist) and the radioligand [ 125I]iodocyanopindolol. The IC 50 values ranged from 5 ± 1 × 10 −8 M (clenbuterol) to 8 ± 2 × 10 −6 M (isoxsuprine) for the β-agonists tested and from 1.5 ± 0.2 × 10 −10 M (carazolol) to 1.2 ± 0.2 × 10 −5 M (metoprolol) for the β-blockers tested. It was shown to have a lower limit of detection than a radio-receptor assay using the solubilised β 2-adrenoceptor expressed in a mammalian cell line. The solubilised recombinant human β 2-adrenoreceptor expressed in E. coli would be a useful tool to develop non radioactive multianalyte screening methods.