High-resolution solution structure of the retinoid X receptor DNA-binding domain.
The retinoid X receptor (RXR) is a member of the nuclear hormone receptor superfamily of transcriptional regulators and plays a central role in the retinoid and, through its ability to heterodimerize with other nuclear hormone receptors, non-steroid signaling pathways. The DNA-binding and recognition functions of RXR are located in a conserved 83 amino acid residue domain that recognizes the consensus sequence AGGTCA. In order to provide a detailed picture of its structure, we have calculated a high-resolution solution structure of the C195A RXRalpha DNA-binding domain. Structures were calculated using 1131 distance and dihedral angle constraints derived from 1H, 13C and 15N NMR spectra. The structures reveal a perpendicularly packed, "loop-helix" fold similar to other nuclear hormone receptor DNA-binding domains and confirm the existence of the C-terminal helix, which was first observed in the low-resolution NMR structure. The C-terminal helix is well formed and is stabilized by packing interactions with residues in the hydrophobic core. The solution structure of RXR is very similar to that determined by X-ray crystallographic studies of the RXR-TR heterodimer complex with DNA, except that in the latter case no electron density was observed for residues corresponding to the C-terminal helix. Other differences between the X-ray and NMR structures occur in the second zinc-binding loop, which is disordered in solution. Heteronuclear 15N NOE measurements suggest that this loop has enhanced flexibility in the free protein.
Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla,, CA 92037, USA.
S M
SM
Holmbeck
M P
MP
Foster
D R
DR
Casimiro
D S
DS
Sem
H J
HJ
Dyson
P E
PE
Wright
D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D017433:Protein Structure, Secondary; D018168:Receptors, Retinoic Acid / Q000737:chemistry*; D047488:Retinoid X Receptors; D014157:Transcription Factors / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014157:Transcription Factors; D004247:DNA; D015032:Zinc