PMID: 9169611May 1, 1997Paper

Allosteric equilibrium model explains steady-state coupling of beta-adrenergic receptors to adenylate cyclase in turkey erythrocyte membranes

The Biochemical Journal
O Ugur, H O Onaran

Abstract

We used a simple experimental approach to clarify some contradictory predictions of the collision coupling and equilibrium models (e.g. ternary complex, two-state ternary complex or quinternary complex), which describe G-protein-mediated beta-adrenergic receptor signalling in essentially different manners. Analysis of the steady-state coupling of beta-adrenoceptors to adenylate cyclase in turkey erythrocyte membranes showed that: (1) in the absence of an agonist, Gpp(NH)p (a hydrolysis-resistant analogue of GTP) can activate adenylate cyclase very slowly; (2) this activity reaches a steady state in approx. 5 h, the extent of activity depending on the concentration of the nucleotide; (3) isoprenaline-activated steady-state adenylate cyclase can be inactivated by propranolol (a competitive antagonist that relaxes the receptor activation), in the presence of Gpp(NH)p (which provides a virtual absence of GTPase) and millimolar concentrations of Mg2+ (the rate of this inactivation is relatively fast); (4) increasing the concentration of Gpp(NH)p can saturate the steady-state activity of adenylate cyclase. The saturated enzyme activity was lower than that induced by isoprenaline under the same conditions. This additional agonist-indu...Continue Reading

Citations

Jun 2, 2012·Journal of Cardiovascular Pharmacology·Emine Demirel-YilmazMehmet Kursat Derici
Jun 4, 2005·Molecular Pharmacology·Ozlem UgurH Ongun Onaran
Jul 15, 2006·The Journal of Physiological Sciences : JPS·Ziya KaygisizMurat Ikizler
Jan 16, 2009·The Journal of Pharmacology and Experimental Therapeutics·A I KayaH O Onaran
Nov 23, 2006·Electrophoresis·Xunli ZhangStephen J Haswell
Aug 6, 2004·Biochemical Pharmacology·David J Roberts, Magali Waelbroeck
Jun 28, 2008·European Journal of Pharmacology·Figen Amber-CicekMehmet Ugur

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