Solubilization and characterization of guanine nucleotide‐sensitive muscarinic agonist binding sites from rat myocardium

Open Access
Publisher Website
Google Scholar
Abstract
1 Muscarinic receptors from rat myocardial membranes may be solubilized by digitonin in good yield at low temperatures in the presence of Mg2+. 2 Under these conditions, up to 60% of the soluble receptors show high affinity binding for the potent agonist [3H]-oxotremorine-M (KA = 109M−1), which is inhibited by 5′-guanylylimido-diphosphate. 3 The muscarinic binding site labelled with [3H]-oxotremorine-M has a higher sedimentation coefficient (13.4 s) than sites labelled with a 3H antagonist in the presence of guanylylimidodiphosphate (11.6 s) and probably represents a complex between the ligand binding subunit of the receptor and a guanine nucleotide binding protein.