Purification and Quality Control PXR is expressed in baculovirus system and purified by an affinity column in combination with FPLC chromatography.The purified protein is greater than 90% homogeneous and contains no detectable proteases, DNase and RNase activity. Shown to bind to DNA as a heterodimer with RXR alpha (Cat.# P1022)- 1000U (1ug) required.
Unit Definition (Activity) 1 unit equals 1 nanogram of purified protein. 100 units are sufficient for a protein-protein interaction assay detected by immuno-blot system.
Applications PXR can be used for gel mobility shift assay, for protein-protein and small molecules-protein interactions assay.
Formulation and Storage The protein is in 20mM Tris-HCl pH7.9,100mM NaCl, 0.2mM EDTA, 1mM DTT and 20% glycerol. Stored at -70°C before use. Avoid repeated freeze thaw cycles.
Background The nuclear pregnane X receptor (PXR; NR1I2) is an important component of the body’s adaptive defense mechanism against toxic substances including foreign chemicals (xenobiotics) (1, 2). PXR is activated by a large number of endogenous and exogenous chemicals including steroids, antibiotics, antimycotics, bile acids, and the herbal antidepressant St. John’s wort (3-7). PXR is known to regulate the expression of several additional genes encoding proteins involved in xenobiotic metabolism, including multidrug resistance protein 1 (MDR1) (8,9), multidrug resistance-associated protein 2 (MRP2) (10,11), and organic anion transporter polypeptide 2 (12). Elucidation of the three-dimensional structure of the PXR ligand binding domain revealed that it has a large, spherical ligand binding cavity that allows it to interact with a wide range of hydrophobic chemicals. Thus, unlike other nuclear receptors that interact selectively with their physiological ligands, PXR serves as a generalized sensor of hydrophobic toxins. PXR binds as a heterodimer with the 9-cis retinoic acid receptor (NR2B) to DNA response elements in the regulatory regions of cytochrome P450 3A monooxygenase genes and a number of other genes involved in the metabolism and elimination of xenobiotics from the body. Although PXR evolved to protect the body, its activation by a variety of prescription drugs represents the molecular basis for an important class of harmful drug-drug interactions (reviewed in 13). Thus, assays that detect PXR activity will be useful in developing safer prescription drugs.
References 1. Waxman DJ (1999) Arch Biochem Biophys 369: 11-23 2. Honkakoski P and Negishi M (2000) Biochem J 347: 321-337 3. Bertilsson G, et al. (1998) Proc Natl Acad Sci USA 95: 12208-12213 4. Blumberg B, et al. (1998) Genes Dev 12: 3195-3205 5. Kliewer SA, et al. (1998) Cell 92: 73-82 6. Lehmann JM, et al. (1998) J Clin Invest 102: 1016-1023 7. Moore LB, et al. (2000) Proc Natl Acad Sci USA 97: 7500-7502 8. Geick A, et al. (2001) J Biol Chem 276: 14581-14587 9. Synold TW, et al. (2001) Nat Med 7: 584-590 10. Dussault I, et al. (2001) J Biol Chem 276: 33309-33312 11. Kast HR, et al. (2002) J Biol Chem 277: 2908-2915 12. Staudinger JL, et al. (2001) Proc Natl Acad Sci USA 98: 3369-3374 13. Orans J, et al. (2005) Mol Endocrin
DISCLAIMER
This products is recommended For RESEARCH USE ONLY and is Not qualified for Use in Diagnostic or Therapeutic Procedures.
