Liver X receptor beta (LXR-β) is a member of the nuclear receptor family of transcription factors. LXR-β is encoded by the NR1H2 gene (nuclear receptor subfamily 1, group H, member 2).[5]
Function
The liver X receptors (LXRs) were originally identified as orphan members of the nuclear receptor superfamily because their ligands were unknown. Like other receptors in the family, LXRs heterodimerize with retinoid X receptor and bind to specific response elements (LXREs) characterized by direct repeats separated by 4 nucleotides. Two genes, alpha (LXRA) and beta, are known to encode LXR proteins.[5][6]
Structure
Crystal structure of human liver X receptor β(LXRβ) forming heterodimer with its partner retinoid X receptor α(RXRα) on its cognate element, an AGGTCA direct repeat spaced by 4 nt shows an extended X-shaped arrangement, with DNA- and ligand-binding domains crossed. The LXRβ core binds DNA via canonical contacts and auxiliary DNA contacts that enhance affinity for the response element.[7]
^Song C, Hiipakka RA, Kokontis JM, Liao S (Jun 1995). "Ubiquitous receptor: structures, immunocytochemical localization, and modulation of gene activation by receptors for retinoic acids and thyroid hormones". Annals of the New York Academy of Sciences. 761 (2): 38–49. Bibcode:1995NYASA.761...38S. doi:10.1111/j.1749-6632.1995.tb31367.x. PMID7625741. S2CID27208069.
^Lou X, Toresson G, Benod C, Suh JH, Philips KJ, Webb P, Gustafsson JA (Mar 2014). "Structure of the retinoid X receptor α-liver X receptor β (RXRα-LXRβ) heterodimer on DNA". Nature Structural & Molecular Biology. 21 (3): 277–81. doi:10.1038/nsmb.2778. PMID24561505. S2CID23226682.
Le Beau MM, Song C, Davis EM, Hiipakka RA, Kokontis JM, Liao S (Mar 1995). "Assignment of the human ubiquitous receptor gene (UNR) to 19q13.3 using fluorescence in situ hybridization". Genomics. 26 (1): 166–8. doi:10.1016/0888-7543(95)80100-Z. PMID7782080.
Shinar DM, Endo N, Rutledge SJ, Vogel R, Rodan GA, Schmidt A (Sep 1994). "NER, a new member of the gene family encoding the human steroid hormone nuclear receptor". Gene. 147 (2): 273–6. doi:10.1016/0378-1119(94)90080-9. PMID7926814.
Hoerer S, Schmid A, Heckel A, Budzinski RM, Nar H (Dec 2003). "Crystal structure of the human liver X receptor beta ligand-binding domain in complex with a synthetic agonist". Journal of Molecular Biology. 334 (5): 853–61. doi:10.1016/j.jmb.2003.10.033. PMID14643652.