| Assay Method Information | |
| | High-Throughput Competitive Fluorescence Polarization (FP) Screening Assay |
| Description: | A high-throughput competitive fluorescence polarization (FP) screening assay (Z-factor, 0.62) was developed based on the direct binding interaction between FITC-MCL-1 SAHBA and MCL-1ΔNΔC (EC50, 14 nM) (FIGS. 1A, 2A, and 3A). A compilation of 71,296 small molecules was screened for the capacity to displace FITC-MCL-1 SAHBA from recombinant MCL-1ΔNΔC (aa 172-327) (FIG. 4). To enrich for MCL-1-selective molecules by detecting binding activity for the BCL-XL subclass of anti-apoptotic proteins, the library was also counterscreened using a competitive FP assay (Z-factor, 0.71) developed based on the direct and selective interaction between FITC-BAD BH3 and BCL-XLΔC (EC50, 26 nM) (FIGS. 1B, 2B, and 3B). Small molecules with an apparent preference for MCL-1ΔNΔC (208 compounds, 0.3% hit rate), as defined both by >50% displacement of the FITC-MCL-1 SAHBA/MCL-1ΔNΔC interaction and a >45% difference in peptide displacement from MCL-1ΔNΔC vs. BCL-XLΔC, were advanced to increasingly stringent confirmatory in vitro binding assays including: (1) repeat single-dose testing of 208 molecules in the differential competitive FP screen; (2) alternative single-dose selectivity screen for 130 confirmed MCL-1-directed antagonists comparing relative displacement of FITC-BID BH3, a dual binder,35 from MCL-1 ΔNΔC vs. BCL-XLΔC; and then (3) dose-responsive competitive binding of the 64 most selective molecules against the FITC-MCL-1 SAHBA/MCL-1 ΔNΔC complex (FIG. 4). |
| Affinity data for this assay | |
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