SOLUBILIZATION AND CHARACTERIZATION OF ACTIVE ANGIOTENSIN II RECEPTORS FROM THE BOVINE ADRENAL CORTEX

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Abstract
Binding sites showing the characteristics of receptors for angiotensin II [AGII] were solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) from bovine adrenal membranes. Binding of 125I-AGII to the solubilized receptor was of high affinity and saturable. AGII analogs inhibited the binding competitively, whereas unrelated peptides did not. Binding activity of the receptor was completely abolished by treatment with the disulfide-reducing agent .beta.-mercaptoethanol. In CHAPS, the receptor formed a complex with 125I-AGII, which is sufficiently stable to permit physicochemical characterization. The CHAPS-solubilized receptor has a Stokes radius of 7.5 nm when measured by gel filtration on Ultrogel AcA 34. On isoelectric focusing, 125I angiotension-receptor complexes gave a major (pI [isoelectric point] = 6.1) and a minor (pI = 4.3) peaks. AGII-bound and free receptors exhibited marked differences in their stability against acid and .beta.-mercaptoethanol. [Implications with respect to the role of this receptor in the regulation of AGII induced aldosterone secretion are presented.].