title: Identification of a novel Mr = 76-kDa form of beta-adrenergic receptors.
abstract: The structure of the human beta-adrenergic receptor in purified basal membranes of human placental syncytiotrophoblast was probed using photoaffinity labeling. Basal membranes display a high specific activity of receptors (4-5 pmol/mg protein) and possess both beta 1- and beta 2-adrenergic receptors subtypes. Autoradiography of membranes that were incubated with the beta-adrenergic antagonist [125I]iodoazidobenzylpindolol, photolyzed and then subjected to sodium dodecylsulfate-polyacrylamide gel electrophoresis, identified four radiolabeled peptides, Mr = 65-kDa, 54-kDa, 43-kDa and a novel higher molecular weight 76-kDa form of the receptor. Photoaffinity labeling of each of these four peptides displayed the pharmacological properties expected for true beta-adrenergic receptors. The 76-kDa photoaffinity labeled receptor peptide observed in human placenta basal membranes has not been reported elsewhere. Competition studies with the beta1-selective ligand CGP-20712A demonstrate that the photoaffinity labeled receptor peptides are composed of both beta 1- and beta 2-adrenergic receptor subtypes.
mesh_terms: D000319:Adrenergic beta-Antagonists; D000345:Affinity Labels; D001386:Azides; D006801:Humans; D007093:Imidazoles / Q000378:metabolism; D008566:Membranes / Q000032:analysis; D008970:Molecular Weight; D010777:Photochemistry; D010869:Pindolol / Q000031:analogs & derivatives; D010920:Placenta / Q000032:analysis; D011943:Receptors, Adrenergic, beta / Q000302:isolation & purification*
chemical_list: D000319:Adrenergic beta-Antagonists; D000345:Affinity Labels; D001386:Azides; D007093:Imidazoles; D011943:Receptors, Adrenergic, beta; C029987:1-(indol-4-yloxy)-3-(1-(4-azido-3-iodophenyl)-2-isobutylamine)-2-propanol; D010869:Pindolol; C049763:CGP 20712A