The important role of residue F268 in ligand binding by LXRβ

FEBS Letters

Urban, Frank¹  Wang, Minghan¹  Dunbar, James²  Cavazos, Gabriel¹  Tafuri, Sherrie¹  Escher, Pascal¹  Tan, Bing¹ 

[1]Department of Molecular Biology, Pfizer Global Research and Development Ann Arbor Laboratories, 2800 Plymouth Road, Ann Arbor, MI 48105, USA

[2]Department of Discovery Technology, Pfizer Global Research and Development Ann Arbor Laboratories, 2800 Plymouth Road, Ann Arbor, MI 48105, USA

关键词: Liver X receptor;    Ligand binding domain;    Scintillation proximity assay;   

DOI  :  10.1016/S0014-5793(00)02130-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Liver X receptors (LXRs) are nuclear receptors that regulate the metabolism of cholesterol and bile acids. Despite information on the specificity of their natural ligands, oxysterols, relatively little is known about the ligand binding site in LXRs. The helix 3 region in the ligand binding domain (LBD) of peroxisome proliferator-activated receptors (PPARs) has been implicated in ligand entry. Sequence alignment of LXRs, farnesoid X receptor (FXR), and PPARs identified the corresponding helix 3 region in the LXRβ LBD. Residues F268 and T272, which are conserved in all the aligned sequences and only in LXRs and FXR, respectively, were replaced with alanine. The effects of these mutations on ligand binding and receptor activation were examined using an in vitro ligand binding assay and a cell based reporter assay, respectively. The LXRβ mutant F268A did not bind ligand. In contrast, conversion of T272 to alanine has no effect on ligand binding. By transiently expressing a chimeric receptor containing Escherichia coli tetracycline repressor (TetR) and LXRβ LBD and a reporter with a TetR binding site, we show that mutant F268A lost the ability to activate transcription of the reporter, whereas mutant T272A still has an activity similar to that of the wild-type LXRβ. These data, consistent with the findings in the in vitro ligand binding assay and our 3D modeling, are the first study that identifies a residue critical for ligand binding in LXRβ.

【 授权许可】

Unknown