Determination of the Molecular Size of Frog and Turkey Erythrocyte β-Adrenergic Receptors by Radiation Inactivation
The β1 and β2-adrenergic receptors from turkey and frog erythrocyte plasma membranes, respectively, have been solubilized with digitonin and purified by sequential affinity and gel-permeation high-performance liquid chromatography. Examination of these preparations after labeling with Na125I/chloramine T or with the photoaffinity reagent 125I-labeled (p-azidobenzyl)carazolol, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, reveals the β-ad-renergic receptor to be composed entirely of Mr 58 000 sub-units. In contrast, for the β1-adrenergic receptor of turkey erythrocytes, two distinct receptor peptides of Mr 40000 and 45 000 were identified. These peptides represent the ligand binding site of these receptors since they interact with adrenergic ligands with the expected β1 and β2 specificity. In this study, in order to examine the functional size of both frog and turkey erythrocyte β-adrenergic receptors, particulate membrane and purified preparations were subjected to irradiation. Under these conditions, a molecular weight of 54000 was obtained for both the membrane-bound and purified β2-ad-renergic receptors of frog erythrocytes. For the β1 receptor from turkey erythrocytes, molecular weights of 41000-53 000 were obtained in the membrane. In purified preparations, a slightly higher value of Mr 54000-55 000 was obtained. These data indicate that the peptides identified as the receptor subunit by purification and photoaffinity labeling contain a single ligand binding site for both the frog erythrocyte β2-adrenergic receptor and the turkey erythrocyte β1-adrenergic receptor. © 1984, American Chemical Society. All rights reserved.
Shorr, RGL; Strohsacker, MW; Nambi, P; Lefkowitz, RJ; Caron, MG; Kempner, ES
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