Protein Expression and Purification, Vol.149, 17-22, 2018
Escherichia coli expression, purification, and refolding of human folate receptor alpha (hFR alpha) and beta (hFR beta)
Human folate receptors (hFR alpha and hFR beta) are membrane proteins anchored to the cell surface by glycosylphosphatidylinositol. They play an important role in cell growth by taking up folate for de novo synthesis of purines and methylation of DNA, lipids, and proteins. Thus, controlling folate uptake through hFRs may lead to the development of anti-cancer drugs. Development of hFRs-targeting drug requires a large amount of hFRs. However, it is difficult to prepare active forms of hFRs from prokaryotic cells because of their high content of cysteine residues that form disulfide bonds. Here, we prepared active forms of hFR alpha and hFR beta from inclusion bodies of Escherichia coli. The crucial steps in our preparation were intensive washing of the inclusion bodies to remove impurities derived from E. coli and gradual dropping of solubilized hFRs into refolding buffers to correctly reform disulfide bonds. The binding activity of prepared hFRs to folate was confirmed by biolayer interferometry measurements. Finally, we successfully prepared the active form of 2.52 mg hFR alpha and 2.4 mg hFR beta from 10 g of E. coli cell bodies.
Keywords:Folate;Human folate receptor alpha (hFR alpha);Human folate receptor beta (hFR beta);Escherichia coli expression;Inclusion body;Intensive washing of inclusion body;Solubilization;Immobilized metal affinity chromatography (IMAC);Gradual dropping refolding;Bio-layer interferometry (BLI)