PXR, or Nuclear receptor subfamily 1 group I member 2, is a human gene encoded by NR1I2. It may also be known as: Orphan nuclear receptor PAR1; Orphan nuclear receptor PXR; Pregnane X receptor; Steroid and xenobiotic receptor; SXR; BXR; ONR1; PAR; PARq; PRR; nuclear receptor subfamily 1, group I, member 2. The encoded protein has an amino acid length of 434 and a mass of 49.8 kDa. PXR is a member of the Nuclear hormone receptor family, NR1 subfamily. Homologs of this gene exist in other organisms, including: Mouse, Rat, Zebrafish, Frog.