title: Solubilization of a mammalian beta-adrenergic receptor.
abstract: Binding sites for iodohydroxybenzylpindolol with characteristics of a beta2-adrenergic receptor have been identified in a crude membrane fraction from guinea-pig lung. The binding sites could be solubilized by treatment of the membrane fraction with digitonin. Upon solubilization receptors retain their beta2-adrenergic type as indicated by the rank order of potencies of agonists in binding-inhibition experiments. The solubilized receptors demonstrate a marked increase in affinity for agonists compared with particulate receptors whereas antagonist affinity remains unchanged. Solubilized receptors are insensitive to divalent cations (Mg2+, Mn2+, Ca 2+) which increase the potency of agonists for particulate receptors. The effects of Mg2+ can be reversed by Gpp(NH)p in particulate preparations; Gpp(NH)p is ineffective for the solubilized preparation. These experiments establish that beta-adrenergic receptors can be solubilized even from crude mammalian membrane preparations. They also show that the mammalian beta-adrenergic receptor in situ is under constraints with respect to agonist affinity and is modulated by divalent cations and guanyl nucleotides in the intact membrane.
mesh_terms: D000262:Adenylyl Cyclases / Q000302:isolation & purification; D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D005260:Female; D006150:Guanine Nucleotides / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008024:Ligands; D008168:Lung / Q000032:analysis; D008566:Membranes / Q000032:analysis; D008722:Methods; D010869:Pindolol / Q000031:analogs & derivatives; D011941:Receptors, Adrenergic / Q000302:isolation & purification*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000302:isolation & purification* / Q000378:metabolism; D012995:Solubility; D013997:Time Factors
chemical_list: D002413:Cations, Divalent; D006150:Guanine Nucleotides; D008024:Ligands; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D010869:Pindolol; D000262:Adenylyl Cyclases