A media for expression of a target protein should be added with an antibiotic for a plasmid selection for the target protein, chloramphenicol (20 μg/ml) for selection of chaperone plasmid, and an expression inducer for chaperone plasmid. When growth inhibition occurs, add the inducer for chaperone gene just before the induction of target protein expression. The species of chaperone and culture conditions (e.g. media, culture temperature, aeration, timing for induction, inducer concentration, induction time) vary depending on the target protein. The optimal culture condition should be determined according to the target protein.
0. Prepare 1 M L-arabinose 0.15 g/mL and 1 M MnCl2 in dH2O and filter it with 0.22 μm filter.
1. Prepare LB broth containing 20 μg/ml chloramphenicol and 100 μg/ml of ampicilin, 1 mM MnCl2 for plasmid expression, and 0.1 mM L-arabinose.
2. Culture the BL21(DE3)/your plasmid/pGro7 with shaking at 37°C.
3. When the OD600 of the culture solution reaches 0.4 - 0.6, leave at 20°C for 30 min.
4. Add IPTG at the final concentration of 0.1 mM, then culture with shaking at 20°C for overnight (ca. 12 hrs).
5. After completion of the culture, verify the expression and solubility of a target protein by SDS-PAGE. GroEL: 60 kDa, GroES: 10 kDa.