| Assay Method Information | |
| | Homogeneous Time Resolved Fluorescence (HTRF) Assay |
| Description: | To determine the potency of compounds for inhibiting nucleotide exchange, various concentrations were incubated with K-Ras G12C (25 nM in reaction, 12.5 nM final). After 18 hours at room temperature, the SOS1 GTP exchange factor (1.67 nM during exchange, 1.25 nM final) was added to initiate nucleotide exchange to GTP (200 μM during exchange, 150 M final). The level of GTP exchange was assessed by addition of a Ras binding domain derived from C-Raf and the HTRF detection antibodies Tb-anti-FLAG and D2-anti-his (Cis-Bio) at 50 nM, 1 nM and 12.5 nM, respectively. After 2 hours, the ratio of 665 nm to 615 nM emission with 320 nM excitation was measured on an Envision plate reader (Perkin Elmer).The final reaction volume was 20l in a ProxiPlate-384F Plus (Perkin Elmer), in buffer containing 20 mM HEPES, 150 mM NaCl, 1 mM MgCl2, 0.1% BSA, 0.03% Tween-20 and 1 mM DTT. K-Ras G12C (residues 2-188) and SOS1 (residues 564-1049) had N-terminal 6-His and the Raf-RBD construct (residues 51-186 of RAFI) had an N-terminal Flag-tag. All constructs were expressed in E. coli and had a Tev cleavage site between the tag and protein of interest that was not used during purification. |
| Affinity data for this assay | |
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