Assay Method Information

Assay Name:  [35S]GTPgammaS Binding Assay
Description:  The frozen cell membrane fraction prepared as described above was thawed before use, and the resultant was diluted with a buffer for a binding assay (final concentrations: 20 mM HEPES, 100 mM NaCl, 1 mM MgCl2, 3 uM GDP, 300 ug/mL saponin, 0.1% BSA). The compound of each example was added to a cell membrane fraction containing 1.8 to 3 ug/assay of membrane protein on a plate, followed by incubation at room temperature for 30 minutes. Thereafter, with glutamic acid (in a final concentration of 10 uM) added thereto, incubation was performed at room temperature for 15 minutes, and thereafter, [35S]GTPγS (in a final concentration of 0.8 kBq) and 588 ug WGA-SPA beads were added thereto, followed by incubation at room temperature for 1 hour. After the incubation, the plate was subjected to the centrifugal separation at 2,500 rpm and room temperature, and then, membrane cell binding radioactivity was measured with a top count. A [35S]GTPγS binding amount obtained in the presence of glutamic acid was defined as specific binding. On the basis of ratios of inhibiting the specific binding at various concentrations of the compounds of the respective examples, inhibition curves were obtained. Concentrations of the compounds of the respective examples at which the specific [35S]GTPγS binding amount was suppressed by 50% (IC50 values) were calculated on the basis of the inhibition curves.
Affinity data for this assay
 

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