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| | TYK2 JH2 Domain Binding Assay |
| Description: | Binding constants for compounds of the present invention against the JH2 domain were determined by the following protocol for a KINOMEscan assay (DiscoveRx). A fusion protein of a partial length construct of human TYK2 (JH2domain-pseudokinase) (amino acids G556 to D888 based on reference sequence NP_003322.3) and the DNA binding domain of NFkB was expressed in transiently transfected HEK293 cells. From these HEK 293 cells, extracts were prepared in M-PER extraction buffer (Pierce) in the presence of Protease Inhibitor Cocktail Complete (Roche) and Phosphatase Inhibitor Cocktail Set II (Merck) per manufacturers' instructions. The TYK2 (JH2domain-pseudokinase) fusion protein was labeled with a chimeric double-stranded DNA tag containing the NFkB binding site (5′-GGGAATTCCC-3′ (SEQ ID NO: 1)) fused to an amplicon for qPCR readout, which was added directly to the expression extract (the final concentration of DNA-tag in the binding reaction is 0.1 nM).Streptavidin-coated magnetic beads (Dynal M280) were treated with a biotinylated small molecule ligand for 30 minutes at room temperature to generate affinity resins the binding assays. The liganded beads were blocked with excess biotin and washed with blocking buffer (SeaBlock (Pierce), 1% BSA, 0.05% Tween 20, 1 mM DTT) to remove unbound ligand and to reduce nonspecific binding.The binding reaction was assembled by combining 16 μl of DNA-tagged kinase extract, 3.8 μl liganded affinity beads, and 0.18 μl test compound (PBS/0.05% Tween 20/10 mM DTT/0.1% BSA/2 μg/ml sonicated salmon sperm DNA)]. Extracts were used directly in binding assays without any enzyme purification steps at a ≥10,000-fold overall stock dilution (final DNA-tagged enzyme concentration <0.1 nM). Extracts were loaded with DNA-tag and diluted into the binding reaction in a two step process. First extracts were diluted 1:100 in 1× binding buffer (PBS/0.05% Tween 20/10 mM DTT/0.1% BSA/2 μg/ml sonicated salmon sperm DNA) containing 10 nM DNA-tag. This dilution was allowed to equilibrate at room temperature for 15 minutes and then subsequently diluted 1:100 in 1× binding buffer. Test compounds were prepared as 111× stocks in 100% DMSO. Kds were determined using an 11-point 3-fold compound dilution series with three DMSO control points. All compounds for Kd measurements are distributed by acoustic transfer (non-contact dispensing) in 100% DMSO. The compounds were then diluted directly into the assays such that the final concentration of DMSO was 0.9%. All reactions performed in polypropylene 384-well plates. Each was a final volume of 0.02 mL. Assays were incubated with shaking for 1 hour at room temperature. Then the beads were pelleted and washed with wash buffer (1×PBS, 0.05% Tween 20) to remove displaced kinase and test compound. The washed based were re-suspended in elution buffer (1×PBS, 0.05% Tween 20, 0.5 μM non-biotinylated affinity ligand) and incubated at room temperature with shaking for 30 minutes. The kinase concentration in the eluates was measured by qPCR. qPCR reactions were assembled by adding 2.5 μL of kinase eluate to 7.5 μL of qPCR master mix containing 0.15 μM amplicon primers and 0.15 μM amplicon probe. The qPCR protocol consisted of a 10 minute hot start at 95° C., followed by 35 cycles of 95° C. for 15 seconds, 60° C. for 1 minute.Test compounds were prepared as 111× stocks in 100% DMSO. Kds were determined using an 11-point 3-fold compound dilution series with three DMSO control points. All compounds for Kd measurements are distributed by acoustic transfer (non-contact dispensing) in 100% DMSO. The compounds were then diluted directly into the assays such that the final concentration of DMSO was 0.9%. The Kds were determined using a compound top concentration of 30,000 nM. Kd measurements were performed in duplicate. |
| Affinity data for this assay | |
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