Specificity of dye-ligand interaction with the polynucleotide binding domain of 1,25-dihydroxyvitamin D3-receptor complexes of chicken intestinal cytosol.

The binding of 1,25-dihydroxyvitamin D3-receptor complexes from chick intestinal cytosol to DNA-cellulose and isolated intestinal nuclei is inhibited by several dye-ligands in a dose-dependent manner. Concentrations of Cibacron blue F3GA, blue dextran, Procion red HE3B, and Green A dye causing 50% competition for receptor binding to DNA-cellulose ranged from 2.8 to 3.6 microM. A structural analogue of the anthraquinone moiety of Cibacron blue F3GA, bromaminic acid, was 111-fold less potent in inhibiting DNA-cellulose binding. Moreover, the inhibitory effects of these dye-ligands is not due to a simple electrostatic effect, since two other polyanions, heparin and poly-L-glutamate, are much less effective. Whereas dye-ligands can cause the release of receptors bound to DNA-cellulose, they do not alter the dissociation of 1,25-dihydroxyvitamin D3 from its receptor nor do they affect the apparent equilibrium binding constant of the receptor or the concentration of available sterol-binding sites. The inhibition of binding by dye-ligands is competitive with respect to DNA-cellulose binding, indicating that the effect of these dyes is at a domain common to polynucleotides.