Human β2-adrenergic receptors expressed in Escherichia coli membranes retain their pharmacological properties

Abstract

The coding region of the gene for the human β2-adrenergic receptor gene was fused to the β-galactosidase gene of the λgt11 expression vector. The Y1089 Escherichia coli strain was lysogenized with this modified vector and transcription of the fusion gene was induced. Expression of this transcription unit was shown by the appearance in the bacteria of proteins of molecular weight higher than that of native β-galactosidase, which are immunoreactive with anti-β-galactosidase antibodies. Production of β2-adrenergic receptors was shown by the presence, on intact bacteria, of binding sites for catecholamine agonists and antagonists possessing a typical β2-adrenergic pharmacological profile. Binding and photoaffinity labeling studies performed on intact E. coli and its membrane fractions showed that these binding sites are located in the inner membrane of the bacteria. Expression of pharmacologically active human β2-adrenergic receptors in E. coli further supports the similar transmembrane organization proposed for bacteriorhodopsin and eukaryotic membrane-embedded receptors coupled to guanine nucleotide-binding regulatory proteins. Moreover, this system should facilitate future analyses of the ligand-binding properties within this family of membrane receptors.