Assay Method Information

Assay Name:  [35S]GTPgammaS Binding Assay
Description:  The human APJ receptor was cloned by polymerase chain reaction and the gene encoding the receptor was subcloned in pFLAG-CMV -3 expression vector (Sigma, Saint Louis, Mo. USA) in-house at Amgen. A GTPγS binding assay was performed on membranes prepared from CHO cells stably expressing human APJ receptor. The optimum experimental conditions for the concentrations of GDP, MgCl2, and NaCl in the assay buffer were initially determined. The assay was performed in assay buffer [20 mM HEPES, pH 7.5, 5 mM MgCl2, and 0.1% (w/v) BSA with 200 mM NaCl, 3 μM GDP] and membranes expressing human APJ receptor/well along with WGA PS beads. The reaction was initiated by addition of 0.2 nM [35S]GTPγS (Perkin Elmer Life and Analytical Sciences, Waltham USA) in the absence or presence of various ligands and incubated at RT for 90 min. Nonspecific binding was determined in the presence of 100 μM GTPγS and was always less than 0.2% of total binding. All the results presented are means of several independent experiments and analyzed by non-linear regression methods using commercially available program Prism (GraphPad, San Diego, Calif.)
Affinity data for this assay
 

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