Recombinant FXR protein
Recombinant FXR is isolated from an E. coli strain that carries the coding sequence of the human FXR under the control of a T7 promoter (accession number U68233). The purified recombinant protein has an amino terminal polyhistidine tag and is greater than 90% homogeneous and contains no detectable protease, DNase and RNase activity. The farnesoid X receptor (FXR) or nuclear receptor subfamily 1, group H, member 4 (NR1H4) is a nuclear receptor that, when activated, translocates to the nucleus where it interacts with certain proteins, including RXR and PPARGC1A, forming heterodimers that bind to hormone response elements on DNA and modulate gene expression. One of the primary functions of FXR is to suppress bile acid synthesis when levels are high by inhibiting the transcription of cholesterol 7 alpha-hydroxylase (CYP7A1) gene that expresses CYP7A1, the rate-limiting enzyme in bile acid synthesis from cholesterol.