Structural properties of the alpha 1-adrenergic receptor: studies with membrane and purified receptor preparations

The contribution of hydrophobic, ionic, and disulfide bonds in the alpha 1-adrenergic receptor structure was evaluated using rat hepatic plasma membrane and purified receptor preparations. In addition, the findings were compared with similar structural evaluations of the beta 2-adrenergic receptor purified from canine lung. Both the alpha 1- and beta 2-adrenergic receptors contain a disulfide bond critical for ligand binding. However, the disulfide bond in the beta-receptor structure is accessible to solvent, while the disulfide bond within the alpha-receptor structure is "masked" and inaccessible to solvent. Reduction of this disulfide bond requires initial denaturation of the alpha 1-receptor. Although the tertiary structures of both receptor proteins appear to be stabilized by strong hydrophobic interactions, differential sensitivities are observed with a variety of structural perturbants, including high concentrations of sodium chloride, guanidine hydrochloride, and ethylene glycol.