Abstract
I analyzed in this work the effect of agonists and unlabeled guanyl nucleotides on [35S]GTPγS and [3H]NMS binding to transfected CHO cells expressing hM1 muscarinic receptors. I was unable to explain my kinetic results by “traditional” (one-site, two-site, or two-step) bimolecular binding models. I therefore examined the equations that describe catalytic G protein activation. My results were fully consistent with the following interpretation: G protein-coupled receptors either interacted with GDP-bound G proteins and facilitated the GDP release or recognized empty G proteins, depending on the incubation conditions. The receptor-coupled empty G proteins (RG) then recognized GTPγS, and the occupied G protein (G
Footnotes
- Received August 8, 2000.
- Accepted January 9, 2001.
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Send reprint requests to: Dr. Waelbroeck, Laboratoire de Chimie Biologique et de la Nutrition, Faculté de Médecine de l'Université Libre de Bruxelles, Bât. G/E, CP 611, 808 Route de Lennik, B–1070 Brussels, Belgium. E-mail:mawaelbr{at}ulb.ac.be
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Supported by Grant 3.4504.99 from the Fonds de la Recherche Scientifique Médicale, by an “Action de Recherche Concertée” from the “Communauté Française de Belgique” and by a “Interuniversity Poles of Attraction Program - Belgian State, Prime Minister's Office - Federal Office for Scientific, Technical and Cultural Affairs”.
- The American Society for Pharmacology and Experimental Therapeutics
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