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.
Holmbeck
S M
SM
Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla,, CA 92037, USA.
Foster
M P
MP
Casimiro
D R
DR
Sem
D S
DS
Dyson
H J
HJ
Wright
P E
PE
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