crystal structure of CAR/RXR heterodimer bound with SRC1 peptide, fatty acid, and 5b-pregnane-3,20-dione.
[RXRA_HUMAN] Receptor for retinoic acid. Retinoic acid receptors bind as heterodimers to their target response elements in response to their ligands, all-trans or 9-cis retinoic acid, and regulate gene expression in various biological processes. The RAR/RXR heterodimers bind to the retinoic acid response elements (RARE) composed of tandem 5'-AGGTCA-3' sites known as DR1-DR5. The high affinity ligand for RXRs is 9-cis retinoic acid. RXRA serves as a common heterodimeric partner for a number of nuclear receptors. The RXR/RAR heterodimers bind to the retinoic acid response elements (RARE) composed of tandem 5'-AGGTCA-3' sites known as DR1-DR5. In the absence of ligand, the RXR-RAR heterodimers associate with a multiprotein complex containing transcription corepressors that induce histone acetylation, chromatin condensation and transcriptional suppression. On ligand binding, the corepressors dissociate from the receptors and associate with the coactivators leading to transcriptional activation. The RXRA/PPARA heterodimer is required for PPARA transcriptional activity on fatty acid oxidation genes such as ACOX1 and the P450 system genes.    [NR1I3_HUMAN] Binds and transactivates the retinoic acid response elements that control expression of the retinoic acid receptor beta 2 and alcohol dehydrogenase 3 genes. Transactivates both the phenobarbital responsive element module of the human CYP2B6 gene and the CYP3A4 xenobiotic response element.
Publication Abstract from PubMed
The X-ray crystal structure of the human constitutive androstane receptor (CAR, NR1I3)/retinoid X receptor alpha (RXRalpha, NR2B1) heterodimer sheds light on the mechanism of ligand-independent activation of transcription by nuclear receptors. CAR contains a single-turn Helix X that restricts the conformational freedom of the C-terminal AF2 helix, favoring the active state of the receptor. Helix X and AF2 sit atop four amino acids that shield the CAR ligand binding pocket. A fatty acid ligand was identified in the RXRalpha binding pocket. The endogenous RXRalpha ligand, combined with stabilizing interactions from the heterodimer interface, served to hold RXRalpha in an active conformation. The structure suggests that upon translocation, CAR/RXRalpha heterodimers are preorganized in an active conformation in cells such that they can regulate transcription of target genes. Insights into the molecular basis of CAR constitutive activity can be exploited in the design of inverse agonists as drugs for treatment of obesity.
A structural basis for constitutive activity in the human CAR/RXRalpha heterodimer.,Xu RX, Lambert MH, Wisely BB, Warren EN, Weinert EE, Waitt GM, Williams JD, Collins JL, Moore LB, Willson TM, Moore JT Mol Cell. 2004 Dec 22;16(6):919-28. PMID:15610735
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.