| Assay Method Information | |
| | Fluorescence Polarization Assay |
| Description: | Expression and purification of the BRD4(I) recognition domain: colonies of newly transformed plasmid DNA from E. coli BL21(DE3)-condon plus-RIL cells were cultivated in 50 mL of Terrific Broth medium containing 50 μg/mL kanamycin and 34 μg/mL chloramphenicol at 37° C. overnight (starting culture). The starting culture was then diluted 100-fold in 1 L of fresh TB medium and the cells were grown at 37° C. to an optical density of about 0.8 at OD600 and then the temperature was lowered to 16° C. When the system was equilibrated at 16° C., the optical density at OD600 was approximately 1.2, and protein expression was induced with 0.2 mmol of isopropyl-β-D-thiogalactopyranoside (IPTG) overnight at 16° C. Bacteria were harvested by centrifugation (4000×g, 20 minutes, 4° C.) and stored as a pellet at −80° C. The cells expressing His 6-tagged protein was resuspend in lysis buffer [50 mmol 4-hydroxyethylpiperazineethanesulfonic acid (HEPES), 25° C., pH 7.5, 500 mmol NaCl, 10 mmol imidazole, 5% glycerol and freshly added 0.5 mmol of tris(2-carboxyethyl)phosphine hydrochloride (TCEP) and 1 mmol of phenylmethanesulfonyl fluoride (PMSF)] and lysed at 4° C. using JN 3000PLUS high pressure homogenizer (JNBIO-Guangzhou, China). The lysate was clarified by centrifugation (12,000×g for 1 hour at 4° C.) and applied to a nickel-nitriloacetate agarose column. The column was washed once with 50 mL of wash buffer containing 30 mmol of imidazole. The protein was eluted using imidazole in an elution buffer in a stepwise elution (100-250 mmol imidazole in 50 mmol HEPES, 25° C., pH 7.5, 500 mmol NaCl, 5% glycerol). All fractions were collected and monitored by SDS-polyacrylamide gel electrophoresis (Bio-Rad Criterion TM Precast Gels, 4-12% Bis-Tris, 1.0 mm, from Bio-Rad, CA). After 1 mmol of dithiothreitol (DTT) was added, the eluted proteins were treated with tobacco plaque virus (TEV) protease overnight at 4° C. to remove the His6 tag. The protein was concentrated and further purified by size exclusion chromatography on a Superdex 75 16/60 HiLoad gel filtration column. The samples were monitored by SDS-polyacrylamide gel electrophoresis and concentrated to 8-10 mg/mL with gel filtration buffer, 10 mmol Hepes pH 7.5, 500 mM NaCl, 1 mmol DTT, and used for protein binding assays and crystallization. |
| Affinity data for this assay | |
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