title: Covalent labeling of the cerebral cortex alpha 1-adrenergic receptor with a new high affinity radioiodinated photoaffinity probe.
abstract: A novel high affinity radioiodinated photoaffinity probe, 4-amino-6,7-dimethoxy-2[4-[5(3-[125I]iodo-4-azidophenyl)pentanoyl]-1- piperazinyl]-quinazoline, structurally related to the potent alpha 1-adrenergic antagonist prazosin, was developed and used to covalently label the rat cerebral cortex alpha 1-adrenergic receptor. In the absence of light, this ligand binds to cortex plasma membranes with a dissociation constant of 308 pM and with a maximal number of binding sites of 200 fmol/mg protein. Upon photolysis, the ligand incorporates irreversibly into plasma membrane proteins. Autoradiograms of such membrane samples subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveal a major specifically labeled polypeptide at Mr = 79,000. The covalent incorporation into the peptide at Mr = 79,000 can be inhibited by several adrenergic receptor ligands with a typical alpha 1-adrenergic receptor specificity and stereoselectivity.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D001386:Azides / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
chemical_list: D000345:Affinity Labels; D001386:Azides; D011942:Receptors, Adrenergic, alpha; C039335:4-amino-6,7-dimethoxy-2-(4-(5-(3-iodo-4-azidophenyl)pentanoyl)-1-piperazinyl)quinazoline