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Curr Pharm Des. 2000 May;6(7):733-48.

Structure-function analysis of vitamin D and VDR model.

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  • 1Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-0062, Japan. yamada@i-mde.tmd.ac.jp

Abstract

In the first section, the general three-dimensional structure of the ligand-binding domain (LBD) of nuclear receptors (NR) was briefly described on the basis of their x-ray crystal structures. Emphasis was placed on the three major conformations of NR-LBD and their role in the transactivation function. In the second part, the structure-function relationship of vitamin D was analyzed based on the ligand structure, in particular by using systematic conformational analysis as a tool. On the basis of the conformational analysis of the vitamin D side chain and studies using conformationally restricted synthetic vitamin D analogs, we suggested the active space region concept of vitamin D: The vitamin D side-chain region was grouped into five regions (A, G, EA, EG and F). Activity orders, in terms of the spatial region, found by these studies are as follows: Affinity for vitamin D receptor (VDR), EA>A>F>G>EG; Affinity for vitamin D binding protein (DBP), A>>G,EA, EG; Target gene transactivation, EA>F>A>EG G; Cell differentiation, EA>F>A>EG G; Bone calcium mobilization, EA>G A>F EG; Intestinal calcium absorption, EA=A G>>EG. In the third section, homology modeling of VDR-LBD and docking of the natural ligand, 1,25-(OH)2D3, into the ligand binding cavity of the model are described. Amino acid residues forming hydrogen bonds with the biologically important 1alpha- and 25-OH groups were identified: 1alpha-OH forms a pincer-type hydrogen bond with R274 and S237 and 25-OH with H397. This VDR-LBD/1,25-(OH)2D3 docking model was firmly substantiated by mutation analysis. Using this VDR model, the structure-function relationship of highly potent vitamin D analogs was discussed.

PMID:
10828304
[PubMed - indexed for MEDLINE]
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