Changes in dynamical behavior of the retinoid X receptor DNA-binding domain upon binding to a 14 base-pair DNA half site.
The retinoid X receptor (RXR) is a prominent member of the nuclear receptor family of ligand-inducible transcription factors. Many proteins of this family exert their function as heterodimers with RXR as a common upstream partner. Studies of the DNA-binding domains of several nuclear receptors reveal differences in structure and dynamics, both between the different proteins and between the free- and DNA-bound receptor DBDs. We investigated the differences in dynamics between RXR free in solution and in complex with a 14 base-pair oligonucleotide, using (1)H and (15)N relaxation studies. Nano- to picosecond dynamics were probed on (15)N, employing Lipari-Szabo analysis with an axially symmetric tumbling model to estimate the exchange contributions to the transverse relaxation rates. Furthermore, milli- to microsecond dynamics were estimated qualitatively for (1)H and (15)N, using CPMG-HSQC and CPMG-T(2) measurements with differential pulse spacing. RXR shows hardly any nano- to picosecond time-scale internal motion. Upon DNA binding, the order parameters show a tiny increase. Dynamics in the milli- to microsecond time scale is more prevalent. It is localized in the first and second zinc fingers of the free RXR. Upon DNA-binding, exchange associated with specific/aspecific DNA-binding of RXR is observed throughout the sequence, whereas conformational flexibility of the D-box and the second zinc finger of RXR is greatly reduced. Since this DNA-binding induced folding transition occurs remote from the DNA in a region which is involved in protein-protein interactions, it may very well be related to the cooperativity of dimeric DNA binding.
Bijvoet Center for Biomolecular Research, NMR Spectroscopy Department, Utrecht University, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
P J
PJ
van Tilborg
M
M
Czisch
F A
FA
Mulder
G E
GE
Folkers
A M
AM
Bonvin
M
M
Nair
R
R
Boelens
R
R
Kaptein
D016880:Anisotropy; D020029:Base Pairing; D001665:Binding Sites; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D004058:Diffusion; D019281:Dimerization; D007700:Kinetics; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D018168:Receptors, Retinoic Acid / Q000737:chemistry* / Q000378:metabolism; D047488:Retinoid X Receptors; D012996:Solutions; D013816:Thermodynamics; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism
D004268:DNA-Binding Proteins; D009587:Nitrogen Isotopes; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D012996:Solutions; D014157:Transcription Factors; D004247:DNA