Residues of the human nuclear vitamin D receptor that form hydrogen bonding interactions with the three hydroxyl groups of 1alpha,25-dihydroxyvitamin D3.
Most of the biological effects of 1,25-dihydroxyvitamin D(3) (hormone D) are mediated through the nuclear vitamin D receptor (VDR). Hormone binding induces conformational changes in VDR that enable the receptor to activate gene transcription. It is known that residues S237 and R274 form hydrogen bonds with the 1-hydroxyl group of hormone D, while residues Y143 and S278, and residues H305 and H397 form hydrogen bonds with the 3-hydroxyl and the 25-hydroxyl groups of the hormone. A series of VDR mutations were constructed (S237A, R274A, R274Q, Y143F, Y143A, S278A, H305A, and H397F; double mutants: S237A/R274A, Y143F/S278A, Y143A/S278A, and H305A/H397F). The relative binding affinities of the wild-type and variant VDRs were assessed. All of the mutants except H397F resulted in lower binding affinity compared to wild-type VDR. Binding to hormone was barely detectable in Y143F, H305A, and H305A/H397F mutants, and undetectable in mutants R274A, R274Q, Y143A, S237A/R274A, and Y143A/S278A, indicating the importance of these residues. Ability to activate gene transcription was also assessed. All of the VDR mutants, except the single mutant S278A, required higher doses of hormone D for half-maximal response. Defining the role of hormone D-VDR binding will lead to a better understanding of the vitamin D signal transduction pathway.
Reddy
Madhuri D
MD
Department of Chemistry, San Jose State University, San Jose, CA 95192-0101, USA. mreddy6@gmail.com
Stoynova
Ludmilla
L
Acevedo
Alejandra
A
Collins
Elaine D
ED
D005786:Gene Expression Regulation; D006801:Humans; D006860:Hydrogen Bonding; D006900:Hydroxylation; D008024:Ligands; D009154:Mutation / Q000235:genetics; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000378:metabolism
D008024:Ligands; D018167:Receptors, Calcitriol; C118756:dihydroxy-vitamin D3; D014807:Vitamin D