| Assay Method Information | |
| | Akt1 TR-FRET assay |
| Description: | His-tagged human recombinant kinase full-length Akt1 expressed in insect cells was purchased form Invitrogen (part number PV 3599). As substrate for the kinase reaction the biotinylated peptide biotin-Ahx-KKLNRTLSFAEPG (C-terminus in amide form) was used which can be purchased e.g. from the company Biosynthan GmbH (Berlin-Buch, Germany). For the assay 50 nl of a 100 fold concentrated solution of the test compound in DMSO was pipetted into a black low volume 384 well microtiter plate (Greiner Bio-One, Frickenhausen, Germany), 2 μl of a solution of Akt1 in assay buffer [50 mM TRIS/HCl pH 7.5, 5 mM MgCl2, 1 mM dithiothreitol, 0.02% (v/v) Triton X-100 (Sigma)] were added and the mixture was incubated for 15 min at 22 °C. to allow prebinding 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 60 min at 22 °C. The concentration of Akt1 in the assay was adjusted depending of the activity of the enzyme lot and was chosen appropriate to have the assay in the linear range, typical enzyme concentrations were in the range of about 0.05 ng/μl (final conc. in the 5 μl assay volume). The reaction was stopped by the addition of 5 μl of a solution of HTRF detection reagents (200 nM streptavidine-XL665 [Cisbio] and 1.5 nM anti-phosho-Serine antibody [Millipore, cat. #35-001] and 0.75 nM LANCE Eu-W 1024 labeled anti-mouse IgG antibody [Perkin Elmer]) in an aqueous EDTA-solution (100 mM EDTA, 0.1% (w/v) bovine serum albumin in 50 mM HEPES/NaOH pH 7.5). The resulting mixture was incubated 1 h at 22 °C. to allow the binding of the biotinylated phosphorylated peptide to the streptavidine-XL665 and the antibodies. Subsequently the amount of phosphorylated substrate was evaluated by measurement of the resonance energy transfer from the anti-mouse-IgG-Eu-Chelate to the streptavidine-XL665. Therefore, the fluorescence emissions at 620 nm and 665 nm after excitation at 350 nm was measured in a HTRF reader, e.g. a Rubystar (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). Normally test compound were tested on the same microtiter plate at 10 different concentrations in the range of 20 μM to 1 nM (20 μM, 6.7 μM, 2.2 μM, 0.74 μM, 0.25 μM, 82 nM, 27 nM, 9.2 nM, 3.1 nM and 1 nM, dilution series prepared before the assay at the level of the 100 fold conc. stock solutions by serial 1:3 dilutions) in duplicate values for each concentration and IC50 values were calculated by a 4 parameter fit using an in-house software. |
| Affinity data for this assay | |
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