| Assay Method Information | |
| | Cbl-b Displacement Assay (Cbl-b Inhibition Assay high) |
| Description: | The ability of candidate compounds to displace a known inhibitor and thereby inhibit Cbl-b activity was measured by monitoring the interaction of Cbl-b with a fluorophore-labeled probe in the presence of the candidate compound. A truncated variant of Cbl-b (UniProt number Q13191; SEQ ID NO:1) containing an Avitag at its N-terminus was co-expressed with BirA biotin ligase and purified using a standard protocol (see Dou et al., Nature Structural and Molecular Biology, 8: 982-987, 2013; Avidity LLC). Fluorescently-labeled inhibitor probe was synthesized and tagged with BODIPY FL (Example 59). Cbl-b displacement assays were performed in a 384-well plate at room temperature in a 10 μL reaction volume by pre-incubating 0.5 nM Cbl-b in an assay buffer containing 20 mM HEPES pH 7.5, 150 mM NaCl, 0.01% Triton X-100, 0.01% BSA and 0.5 mM TCEP in the presence of a candidate compound in 1% DMSO (final concentration) for 1 hour. After incubation in the presence of the candidate compound, the plate was incubated for an additional 1 hour in the presence of an approximate EC40 binding saturation consisting of 150 nM fluorescently-labeled inhibitor probe and 2 nM Streptavidin-Terbium (Cisbio) (final concentrations). Following the 1 hour incubation, the plates were read for TR-FRET signal at 520/620 nM using an Envision plate reader (Perkin Elmer). The presence of a TR-FRET signal indicated that the probe was not displaced from Cbl-b by the compound candidate. The absence of a FRET signal indicated that the probe was displaced from Cbl-b by the compound candidate. |
| Affinity data for this assay | |
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