Role of residues 143 and 278 of the human nuclear Vitamin D receptor in the full-length and Delta165-215 deletion mutant.
Most of the actions of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] are mediated by binding to the Vitamin D nuclear receptor (VDR). The crystal structure of a deletion mutant (Delta165-215) of the VDR ligand-binding domain (LBD) bound to 1,25(OH)(2)D(3) indicates that amino acid residues tyrosine-143 and serine-278 form hydrogen bonding interactions with the 3-hydroxyl group of 1,25(OH)(2)D(3). Studies of VDR and three mutants (Y143F, S278A, and Y143F/S278A) did not indicate any differences in the binding affinity between the variant receptors and the wild-type receptor. This might indicate that the 3-hydroxyl group binds differently to the full-length VDR than the to deletion mutant. To further investigate, four deletion VDR mutants were constructed: VDR(Delta165-215), VDR(Delta165-215) (Y143F), VDR(Delta165-215) (S278A), VDR(Delta165-215) (Y143F/S278A). There were no significant differences in binding affinity between the wild-type receptor and the deletion mutants except for VDR(Delta165-215) (Y143F/S278A). In gene activation assays, VDR constructs with the single mutation Y143F and the double mutation Y143F/S278A, but not the single mutation S278A required higher doses of 1,25(OH)(2)D(3) for half-maximal response. This suggests that there are some minor structural and functional differences between the wild-type VDR and the Delta165-215 deletion mutant and that Y143 residue is more important for receptor function than residue S278.
Acevedo
Alejandra
A
Department of Chemistry, San Jose State University, San Jose, CA 95192-0101, USA.
Stoynova
Ludmilla
L
Davis
Karen
K
Solórzano
Ramona
R
Collins
Elaine D
ED
D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D017931:DNA Primers; D006801:Humans; D008024:Ligands; D009154:Mutation; D011485:Protein Binding; D018167:Receptors, Calcitriol / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
D017931:DNA Primers; D008024:Ligands; D018167:Receptors, Calcitriol