title: Ligand-specific structural changes in the vitamin D receptor in solution.
abstract: Vitamin D receptor (VDR) is a member of the nuclear hormone receptor superfamily. When bound to a variety of vitamin D analogues, VDR manifests a wide diversity of physiological actions. The molecular mechanism by which different vitamin D analogues cause specific responses is not understood. The published crystallographic structures of the ligand binding domain of VDR (VDR-LBD) complexed with ligands that have differential biological activities have exhibited identical protein conformations. Here we report that rat VDR-LBD (rVDR-LBD) in solution exhibits differential chemical shifts when bound to three ligands that cause diverse responses: the natural hormone, 1,25-dihydroxyvitamin D(3) [1,25(OH)₂D₃], a potent agonist analogue, 2-methylene-19-nor-(20S)-1,25-dihydroxyvitamin D₃ [2MD], and an antagonist, 2-methylene-(22E)-(24R)-25-carbobutoxy-26,27-cyclo-22-dehydro-1α,24-dihydroxy-19-norvitamin D₃ [OU-72]. Ligand-specific chemical shifts mapped not only to residues at or near the binding pocket but also to residues remote from the ligand binding site. The complexes of rVDR-LBD with native hormone and the potent agonist 2MD exhibited chemical shift differences in signals from helix-12, which is part of the AF2 transactivation domain that appears to play a role in the selective recruitment of coactivators. By contrast, formation of the complex of rVDR-LBD with the antagonist OU-72 led to disappearance of signals from residues in helices-11 and -12. We present evidence that disorder in this region of the receptor in the antagonist complex prevents the attachment of coactivators.
authors: National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
authors: Kiran K
authors: KK
authors: Singarapu
authors: Jinge
authors: J
authors: Zhu
authors: Marco
authors: M
authors: Tonelli
authors: Hongyu
authors: H
authors: Rao
authors: Fariba M
authors: FM
authors: Assadi-Porter
authors: William M
authors: WM
authors: Westler
authors: Hector F
authors: HF
authors: DeLuca
authors: John L
authors: JL
authors: Markley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D050071:Bone Density Conservation Agents / Q000737:chemistry / Q000378:metabolism; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D030562:Databases, Protein; D008024:Ligands; D056913:Mediator Complex Subunit 1 / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D051381:Rats; D018167:Receptors, Calcitriol / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012995:Solubility
chemical_list: C468519:2-methylene-1,25-dihydroxy-19-norvitamin D3; C519954:2-methylene-19-nor-(20S)-1alpha,25-dihydroxyvitamin D3; D050071:Bone Density Conservation Agents; D008024:Ligands; D056913:Mediator Complex Subunit 1; D010446:Peptide Fragments; D018167:Receptors, Calcitriol; D011993:Recombinant Fusion Proteins; D002117:Calcitriol