| Assay Method Information | |
| | TBK1 Low ATP Kinase Assay |
| Description: | Recombinant full-length N-terminally His-tagged human TBK1, expressed in insect cells and purified by Ni-NTA affinity chromatography, was purchased from Life Technologies (Cat. No PR5618B) and used as enzyme. As substrate for the kinase reaction biotinylated peptide biotin-Ahx-GDEDFSSFAEPG (C-terminus in amide form) was used which can be purchased e.g. from the company Biosyntan (Berlin-Buch, Germany).For the assay 50 nl of a 100-fold concentrated solution of the test compound in DMSO was pipetted into either a black low volume 384well microtiter plate or a black 1536well microtiter plate (Greiner Bio-One, Frickenhausen, Germany), 2 μl of a solution of TBK1 in aqueous assay buffer [50 mM HEPES pH 7.0, 10 mM MgCl2, 1.0 mM dithiothreitol, 0.05% (w/v) bovine serum albumine, 0.01% (v/v) Nonidet-P40 (Sigma), protease inhibitor mixture ( Complete w/o EDTA from Roche, 1 tablet per 5 ml)] were added and the mixture was incubated for 15 min at 22° C. to allow pre-binding of the test compounds to the enzyme before the start of the kinase reaction. Then the kinase reaction was started by the addition of 3 μl of a solution of adenosine-tri-phosphate (ATP, 16.7 μM=>final conc. in the 5 μl assay volume is 10 μM) and substrate (1.67 μM=>final conc. in the 5 μl assay volume is 1 μM) in assay buffer and the resulting mixture was incubated for a reaction time of 30 min at 22° C. The concentration of TBK1 was adjusted depending of the activity of the enzyme lot and was chosen appropriate to have the assay in the linear range, a typical concentration is 0.03 μg/ml. The reaction was stopped by the addition of 3 μl of a solution of TR-FRET detection reagents (0.33 μM streptavidine-XL665 [Cisbio Bioassays, Codolet, France], 2.5 nM anti-phosho-Serine anti-body [Merck Millipore, STK antibody , cat. #35-C2] and 1.25 nM LANCE EU-W1024 labeled anti-mouse IgG anti-body [Perkin-Elmer, product no. AD0077]) in an aqueous EDTA-solution (167 mM EDTA, 0.13% (w/v) bovine serum albumin in 100 mM HEPES/NaOH pH 7.5).The resulting mixture was incubated 1 h at 22° C. to allow the formation of complex between the phosphorylated biotinylated peptide and the detection reagents. Subsequently the amount of phosphorylated substrate was evaluated by measurement of the resonance energy transfer from the Eu-chelate to the streptavidine-XL. Therefore, the fluorescence emissions at 620 nm and 665 nm after excitation at 350 nm was measured in a TR-FRET reader, e.g. a Pherastar (BMG Labtechnologies, Offenburg, Germany) or a Viewlux (Perkin-Elmer). The ratio of the emissions at 665 nm and at 622 nm was taken as the measure for the amount of phosphorylated substrate. The data were normalised (enzyme reaction without inhibitor=0% inhibition, all other assay components but no enzyme=100% inhibition). Usually the test compounds were tested on the same microtiterplate in 11 different concentrations in the range of 20 μM to 0.07 nM (20 μM, 5.7 μM, 1.6 μM, 0.47 μM, 0.13 μM, 38 nM, 11 nM, 3.1 nM, 0.9 nM, 0.25 nM and 0.07 nM, the dilution series prepared separately before the assay on the level of the 100 fold concentrated solutions in DMSO by serial dilutions, exact concentrations may vary depending pipettors used)) in duplicate values for each concentration and IC50 values were calculated using Genedata Screener software. |
| Affinity data for this assay | |
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