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Updated: Jun 1, 2026

Measuring G-protein-coupled Receptor Signaling via Radio-labeled GTP Binding
Published on: June 9, 2017
Quantifying the activation of the small molecular weight G-protein ras
Katharine Chapman1, David J Hall
1Chemistry Department, Lawrence University, Appleton, Wisconsin 54912.
Abstract:
Low molecular weight guanine-nucleotide binding proteins are molecular switches involved in a wide range of cellular functions in eukaryotes. Ras is activated when a membrane receptor is bound by a ligand and the GDP bound to the Ras protein is exchanged for GTP. Once GTP is bound, the Ras three-dimensional conformation changes and binds the kinase Raf. This protein-protein interaction can be used to "pull-down" activated Ras from a cell lysate. The amount of activated Ras is quantitated through immunoblotting and densitometry. This procedure is excellent as a multiweek investigational laboratory.
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