One-step metal affinity purification of recombinant hFGF19 without using tags

Human fibroblast growth factor 19 (hFGF19) belongs to the endocrine FGF19 superfamily and is considered a potential agent to treat severe or relapsing nonalcoholic fatty liver disease. Numerous studies have confirmed the beneficial effects of this hormone on the related symptoms of the disease and attempts at producing recombinant proteins in various hosts are steadily proliferating. Recently, we reported that authentic hFGF19 can be solubly expressed through combining synonymous codon substitutions and co-expression with disulfide-bond isomerase (DsbC) in Escherichia coli. However, during purification, hFGF19 without the His-tag occasionally co-eluted with His-tagged DsbC when using metal affinity chromatography, thereby requiring auxiliary purification steps to achieve apparent homogeneity. This phenomenon provides evidence that hFGF19 specifically interacts with immobilized Ni²⁺, which can thus be used as an alternative tool for the purification of hFGF19. Consequently, we could simply and reproducibly purify hFGF19 from cell lysates by using Ni²⁺-immobilized metal affinity chromatography and stepwise gradient elution with imidazole.