| 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. | | Synonym | NR1I2; BXR; ONR1; PAR; PAR1; PAR2; PARq; PRR;SAR and SXR | | Protein Sequence | MEVRPKESWN HADFVHCEDT ESVPGKPSVN ADEEVGGPQI CRVCGDKATG YHFNVMTCEG
CKGFFRRAMK RNARLRCPFR KGACEITRKT RRQCQACRLR KCLESGMKKE MIMSDEAVEE
RRALIKRKKS ERTGTQPLGV QGLTEEQRMM IRELMDAQMK TFDTTFSHFK NFRLPGVLSS
GCELPESLQA PSREEAAKWS QVRKDLCSLK VSLQLRGEDG SVWNYKPPAD SGGKEIFSLL
PHMADMSTYM FKGIISFAKV ISYFRDLPIE DQISLLKGAA FELCQLRFNT VFNAETGTWE
CGRLSYCLED TAGGFQQLLL EPMLKFHYML KKLQLHEEEY VLMQAISLFS PDRPGVLQHR
VVDQLQEQFA ITLKSYIECN RPQPAHRFLF LKIMAMLTEL RSINAQHTQR LLRIQDIHPF
ATPLMQELFG ITGS | | 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 | | Image of SDS-PAGE /Western-blot | |
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