| Assay Method Information | |
| | Biochemical Assay |
| Description: | The ability of the receptor interacting protein kinase (RIPK1) to catalyze the hydrolysis of adenosine-5′-triphosphate (ATP) is monitored using the Transcreener ADP (adenosine-5′-diphosphate) assay (BellBrook Labs). Purified human RIP1 kinase domain (2-375) (50 nM) derived from a baculovirus-infected insect cell expression system is incubated with test compounds for 2 hours in 50 mM Hepes buffer (pH 7.5) containing 30 mM MgCl2, 1 mM dithiothreitol, 50 uM ATP, 0.002% Brij-35, and 0.5% dimethyl sulfoxide (DMSO). Reactions are quenched by the addition of 1× Bell Brooks Stop buffer B (20 mM Hepes (ph7.5), 40 mM ethylenediaminetetraacetic acid and 0.02% Brij-35) containing an additional 12 mM EDTA and 55 ug/mL ADP2 antibody and 4 nM ADP-AlexaFluor 633 tracer. The tracer bound to the antibody is displaced by the ADP generated during the RIP1K reaction, which causes a decrease in fluorescence polarization that is measured by laser excitation at 633 nm with a FP microplate reader M1000. Fractional activity was plotted against test article concentration. Using Genedata Screener software (Genedata; Basel, Switzerland), the data were fit to the tight-binding apparent inhibition constant (Ki app) Morrison equation [Williams, J. W. and Morrison, J. F. (1979) The kinetics of reversible tight-binding inhibition. Methods Enzymol 63: 437-67]. The following equation was used to calculate fractional activity and Ki app:Fractional activity = V i V o = 1 - ( [ E ] T + [ I ] T + K i app ) - ( [ E ] T + [ I ] T + K i app ) 2 - 4 [ E ] T [ I ] T 2 [ E ] Twhere [E]T and [I]T are the total concentrations of active enzyme and test article, respectively. |
| Affinity data for this assay | |
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