Genetic analysis of the molecular basis for beta-adrenergic receptor subtype specificity.
Pharmacological analysis of ligand binding to the beta-adrenergic receptor (beta AR) has revealed the existence of two distinct receptor subtypes (beta 1 and beta 2) which are the products of different genes. The predicted amino acid sequences of the beta 1 and beta 2 receptors differ by 48%. To identify the regions of the proteins responsible for determining receptor subtype, chimeras were constructed from domains of the human beta 1 and hamster beta 2 receptors. Analysis of the ligand-binding characteristics of these hybrid receptors revealed that residues in the middle portion of the beta AR sequence, particularly around transmembrane regions 4 and 5, contribute to the subtype specific binding of agonists. Smaller molecular replacements of regions of the hamster beta 2 AR with the analogous regions from the avian beta 1 AR, however, failed to identify any single residue substitution capable of altering the subtype specificity of the receptor. These data indicate that, whereas sequences around transmembrane regions 4 and 5 may contribute to conformations which influence the ligand-binding properties of the receptor, the subtype-specific differences in amine-substituted agonist binding cannot be attributed to a single molecular interaction between the ligand and any amino acid residue which is divergent between the beta 1 and beta 2 receptors.
Dixon
R A
RA
Department of Molecular Biology, Merck, Sharp and Dohme Research Laboratories, West Point, Pennsylvania 19486.
Hill
W S
WS
Candelore
M R
MR
Rands
E
E
Diehl
R E
RE
Marshall
M S
MS
Sigal
I S
IS
Strader
C D
CD
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D006224:Cricetinae; D004247:DNA / Q000096:biosynthesis; D006801:Humans; D008969:Molecular Sequence Data; D010641:Phenotype; D011943:Receptors, Adrenergic, beta / Q000235:genetics*; D011994:Recombinant Proteins; D014422:Turkeys
D011943:Receptors, Adrenergic, beta; D011994:Recombinant Proteins; D004247:DNA