Swamy N, Mohr S C, Xu W, Ray R
Vitamin D Laboratory, Boston University School of Medicine, Boston, Massachusetts, 02118, USA.
Arch Biochem Biophys. 1999 Mar 15;363(2):219-26. doi: 10.1006/abbi.1998.1079.
Vitamin D receptor (VDR) regulates the expression of vitamin D-dependent genes upon binding to its cognate ligand, 1alpha, 25-dihydroxyvitamin D3 (1,25(OH)2D3). This process represents a complex interaction of ligand-bound VDR with nuclear proteins like retinoid X receptor, nuclear accessory factors, and regulatory elements of the target gene. Expression of full-length VDR in Escherichia coli revealed that VDR binds DnaK, a member of heat-shock protein (Hsp) family, with high affinity. By systematic N-terminal truncation of VDR, the interaction site of DnaK on VDR was localized within a 17-amino-acid segment (105-122) representing the "hinge region" between the DNA-binding and hormone-binding domains of VDR. The putative DnaK-binding site was further localized between residues 105 to 109 of VDR by using binding-energy-minimization studies. The interaction of DnaK with VDR did not influence the binding of 1,25(OH)2D3 or nuclear accessory factor(s) to VDR. Furthermore, bovine brain Hsp 70, similar to DnaK, interacted with VDR-ligand-binding domain (105-427). These results suggest that DnaK/Hsp 70 may interact with VDR prior to the activation of the latter by 1,25(OH)2D3-binding.
维生素D受体（VDR）与同源配体1α，25 - 二羟基维生素D3（1,25(OH)2D3）结合后可调节维生素D依赖性基因的表达。这一过程体现了配体结合的VDR与核蛋白（如视黄酸X受体、核辅助因子和靶基因调控元件）之间的复杂相互作用。在大肠杆菌中全长VDR的表达显示，VDR与热休克蛋白（Hsp）家族成员DnaK具有高亲和力结合。通过对VDR进行系统性的N端截短，DnaK在VDR上的相互作用位点定位于一个17个氨基酸的片段（105 - 122）内，该片段代表VDR的DNA结合域和激素结合域之间的“铰链区”。通过结合能最小化研究，推定的DnaK结合位点进一步定位于VDR的105至109位残基之间。DnaK与VDR的相互作用并不影响1,25(OH)2D3或核辅助因子与VDR的结合。此外，牛脑Hsp 70与DnaK类似，可与VDR配体结合域（105 - 427）相互作用。这些结果表明，在1,25(OH)2D3结合激活VDR之前，DnaK/Hsp 70可能就已与VDR相互作用。
