The hydrophobic tryptic core of the porcine alpha 2-adrenergic receptor retains allosteric modulation of binding by Na+, H+, and 5-amino-substituted amiloride analogs.
Extensive trypsinization of the purified alpha 2-adrenergic receptor and repurification by wheat germ agglutinin-agarose chromatography yields an adrenergic ligand-binding hydrophobic core of the receptor. Allosteric modulation of adrenergic ligand binding by Na+, H+, and 5-amino-substituted analogs of amiloride is quantitatively retained in this core, as assessed by the ability of these agents to accelerate the rate of [3H] yohimbine dissociation from the adrenergic ligand-binding site. These findings refine our understanding of where within the alpha 2-adrenergic receptor structure these allosteric agents bind and, for the effects of Na+ and H+, allow certain predictions to be made as to which carboxylic acid side chains are probable candidates for participation in a monovalent cation-binding pocket within the hydrophobic tryptic core of the receptor.
Wilson
A L
AL
Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6600.
Guyer
C A
CA
Cragoe
E J
EJ
Limbird
L E
LE
D000494:Allosteric Regulation; D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010446:Peptide Fragments / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013552:Swine; D014357:Trypsin
D010446:Peptide Fragments; D011942:Receptors, Adrenergic, alpha; D000584:Amiloride; D012964:Sodium; D014357:Trypsin