Fibroblast growth factor 19 (FGF19) is a member of the endocrine fibroblast growth factor family, secreted in the small intestine. FGF19 binds to the fibroblast growth factor receptor 4 (FGFR4) in the presence of β klotho to downregulate the secretion of bile acid. All endocrine FGFs, including FGF19 are unstable. In this study, we examine structure, stability, and bioactivity using a wide range of biophysical and biochemical experiments. The protein has been successfully overexpressed in Escherichia coli (E. coli), and optimal conditions for storage have been established. Results of thermal denaturation of recombinant FGF19, using circular-dichroism and differential scanning calorimetry, suggest that the thermal unfolding of the protein is reversible, and the Tm (melting temperature; temperature at which half of the protein is denatured) was found to be 55 oC. Far UV circular-dichroism data indicate that the backbone of the protein is predominantly in the beta-sheet conformation. In addition, cell proliferation and cell metabolism data show that FGF19 exhibits low cell proliferation, but significant metabolic activity. These results will be discussed in details.
