| Assay Method Information | |
| | High ATP Kinase Assay |
| Description: | A recombinant tagged FGFR-1 fusion protein [fusion of glutathione-S-transferase (GST) (N-terminally), His6-tag, thrombin cleavage site, and the intracellular part of human FGFR-1 from amino acids G400 to R800 as in GenBank entry NM_015850], expressed in SF9 insect cells using baculovirus expression system and purified via glutathione-agarose affinity chromatography, was purchased from Proqinase (product no. 0101-0000-1) and used as enzyme. As substrate for the kinase reaction, the biotinylated peptide biotin-Ahx-AAEEEYFFLFAKKK (C-terminus in amide form) was used which can be purchased, e.g., from Biosyntan (Berlin-Buch, Germany). Usually, test compounds were tested on the same microtiter plate at 11 different concentrations in the range of 20 uM to 0.1 nM (e.g. 20 uM, 5.9 uM, 1.7 uM, 0.51 uM, 0.15 uM, 44 nM, 13 nM, 3.8 nM, 1.1 nM, 0.33 nM, and 0.1 nM) in duplicates for each concentration. The dilution series was prepared separately prior to the assay as 100-fold concentrated stock solutions in DMSO; exact concentrations could vary depending on the pipettor used. For the assay, 50 nl of each stock solution of the test compound in DMSO was pipetted into a black, low-volume 384-well microtiter plate (Greiner Bio-One, Frickenhausen, Germany). 2 ul of a solution of the above FGFR-1 fusion protein in aqueous assay buffer [8 mM MOPS pH 7.0, 10 mM magnesium acetate, 1.0 mM dithiothreitol, 0.05% (w/v) bovine serum albumin (BSA), 0.07% (v/v) Tween-20, 0.2 mM EDTA] was added, and the mixture was incubated for 15 min at 22° C. to allow pre-binding of the test compound to the enzyme. Then, the kinase reaction was started by the addition of 3 ul of a solution of adenosine triphosphate (ATP, 3.3 mM; final concentration in the 5 ul assay volume=2 mM) and substrate (0.16 uM; final concentration in the 5 ul assay volume=0.1 uM) in assay buffer, and the resulting mixture was incubated for a reaction time of 15 min at 22° C. The concentration of FGFR-1 fusion protein was adjusted depending on the activity of the enzyme lot and was chosen appropriately to have the assay in the linear range (typical concentrations were in the range of 0.05 ug/ml). The reaction was stopped by the addition of 5 ul of a solution of HTRF detection reagents [25 nM streptavidin-XL665 (Cis Biointernational) and 1 nM PT66-Eu-chelate, an europium-chelate labelled anti-phosphotyrosine antibody (Perkin-Elmer; PT66-Tb-cryptate from Cis Biointernational may be used instead), in an aqueous EDTA solution (50 mM EDTA, 0.1% (w/v) BSA in 50 mM HEPES/NaOH pH 7.5)]. The resulting mixture was incubated for 1 h at 22° C. to allow formation of the 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 streptavidin-XL665. For this, the fluorescence emissions at 620 nm and 665 nm after excitation at 350 nm were measured in a TR-FRET reader [e.g. Rubystar (BMG Labtechnologies, Offenburg, Germany) or Viewlux (Perkin-Elmer)]. The ratio of the emissions at 665 nm and at 620 nm was taken as the measure for the amount of phosphorylated substrate. Data were normalised (enzyme reaction without inhibitor=0% inhibition, all other assay components but no enzyme=100% inhibition), and IC50 values were calculated by a 4-parameter fit using an in-house software. |
| Affinity data for this assay | |
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