Assay Method Information

Assay Name:  USP19 Activity Assay
Description:  USP19 activity was monitored in a fluorescence polarisation (FP) homogeneous assay using the isopeptide Ubiquitin-Lys-TAMRA substrate (either AUB-101, Almac Sciences Scotland Limited, or U-558, Boston Biochem, both of which gave identical results). Full-length USP19 was purchased from Boston Biochem (E-576). Unless otherwise stated, all other reagents were purchased from Sigma. Enzymatic reactions were conducted in black flat bottom polystyrene 384-well plates (Nunc) and 30 μL total volume. USP19 (2.5 nM, 10 μL) was incubated in assay buffer (50 mM HEPES (pH 7.4), 150 mM NaCl, 5 mM DTT, 0.05% BSA (w/v), 0.05% CHAPS) in the presence or absence of inhibitor (10 μL). Inhibitors were stored as 10 mM DMSO stocks in an inert environment (low humidity, dark, low oxygen, room temperature) using the Storage Pod System and serial dilutions were prepared in buffer just prior to the assay (from 200 μM to 2 pM, 8-18 data point curve). Following incubation at RT for 30 min, the enzymatic reactions were initiated by dispensing the Ub substrate (500 nM, 10 μL). FP was measured every 15 min over a period of 90 min (within the linear range of the assay) using a Synergy 4 plate reader (BioTek) exciting at 530 nm and measuring the amount of parallel and perpendicular light at 575 nm. The FP signal was subsequently normalised to the no compound control. Data were plotted and fitted, and the concentrations resulting in 50% inhibition (IC50) were calculated using the non-linear regression curve fitting model using GraphPad (Prism).
Affinity data for this assay
 

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