Selective binding of ligands to beta 1, beta 2 or chimeric beta 1/beta 2-adrenergic receptors involves multiple subsites.
The molecular basis of ligand binding selectivity to beta-adrenergic receptor subtypes was investigated by designing chimeric beta 1/beta 2-adrenergic receptors. These molecules consisted of a set of reciprocal constructions, obtained by the exchange between the wild-type receptor genes of one to three unmodified transmembrane regions, together with their extracellular flanking regions. Eight different chimeras were expressed in Escherichia coli and studied with selective beta-adrenergic ligands. The evaluation of the relative effect of each chimeric exchange on ligand binding affinity was based on the analysis of delta G values, calculated from the equilibrium binding constants, as a function of the number of substituted beta 2-adrenergic receptor transmembrane domains. The data showed that the contribution of each exchanged region to subtype selectivity varies with each ligand; moreover, while several regions are critical for the pharmacological selectivity of all ligands, others are involved in the selectivity of only some compounds. The selectivity displayed by beta-adrenergic compounds towards beta 1 or beta 2 receptor subtypes thus results from a particular combination of interactions between each ligand and each of the subsites, variably distributed over the seven transmembrane regions of the receptor; these subsites are presumably defined by the individual structural properties of the ligands.
Marullo
S
S
Laboratoire de Biologie Moléculaire des Récepteurs, CNRS, Université Paris VII, Institut Pasteur, France.
Emorine
L J
LJ
Strosberg
A D
AD
Delavier-Klutchko
C
C
D000318:Adrenergic beta-Agonists / Q000378:metabolism; D000319:Adrenergic beta-Antagonists / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D004926:Escherichia coli / Q000378:metabolism; D004983:Ethanolamines / Q000378:metabolism; D007093:Imidazoles / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009638:Norepinephrine / Q000378:metabolism; D017265:Procaterol; D011412:Propanolamines; D015202:Protein Engineering; D011943:Receptors, Adrenergic, beta / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D004983:Ethanolamines; D007093:Imidazoles; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D011993:Recombinant Fusion Proteins; C026777:ICI 118551; C049763:CGP 20712A; D009638:Norepinephrine; D017265:Procaterol