SRC2-3 binds to vitamin D receptor with high sensitivity and strong affinity

Vitamin D receptor (VDR) is a member of the nuclear receptor superfamily and regulates the expression of target genes through ligand binding. To express the target gene, coactivator binding to the VDR/ligand complex is essential. Although there are many coactivators in living cells, precise interactions between coactivators and VDR have not been clarified. Here, we synthesized two coactivator peptides, DRIP205-2 and SRC2-3, evaluated their affinity for the ligand-binding domain (LBD) of VDR using 1α,25-dihydroxyvitamin D3, partial agonist 1, and antagonist 2 by surface plasmon resonance (SPR), and assessed their interaction modes with VDR-LBD using X-ray crystallographic analysis. This study showed that the SRC2-3 peptide is more sensitive to the ligands (agonist, partial agonist, and antagonist) and shows more intimate interactions with VDR-LBD than DRIP205-2 peptide.