TY - JOUR T1 - Covalent labeling of the beta-adrenergic ligand-binding site with para-(bromoacetamidyl)benzylcarazolol. A highly potent beta-adrenergic affinity label. JF - Molecular Pharmacology JO - Mol Pharmacol SP - 499 LP - 506 VL - 27 IS - 5 AU - K E Dickinson AU - S L Heald AU - P W Jeffs AU - R J Lefkowitz AU - M G Caron Y1 - 1985/05/01 UR - http://molpharm.aspetjournals.org/content/27/5/499.abstract N2 - para-(Bromoacetamidyl)benzylcarazolol (pBABC) was synthesized and found to be an extremely potent affinity label for beta-adrenergic receptors. Its interaction with mammalian (rabbit and hamster lung) and nonmammalian (turkey and frog erythrocyte) beta-adrenergic receptors was similar, displaying EC50 values of 400-900 pM for inhibiting 125I-cyanopindolol binding to these receptors. pBABC reduced the number of beta-adrenergic receptors in frog erythrocyte membranes, without any change in the affinity of the remaining sites for [125I]iodocyanopindolol. pBABC has been radioiodinated. As assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, this affinity probe specifically labeled the beta-adrenergic peptide of a purified preparation of hamster lung, with high efficiency (approximately 40%) and with a pharmacological specificity characteristic of an interaction at the beta 2-adrenergic receptor ligand-binding site. Comparison of the proteolyzed products derived from purified receptor labeled with [125I]pBABC and with the photoaffinity agent [125I]p-azidobenzylcarazolol suggested that covalent labeling of the beta-adrenergic receptor by these probes occurs at similar domains of the beta-adrenergic receptor. Because of the much higher level of incorporation of this affinity probe as opposed to photosensitive probes, pBABC should prove to be a useful tool for structural studies of purified beta-adrenergic receptors. ER -