Effect of pyridoxal 5'-phosphate on oligodeoxynucleotide binding of mouse uterine cytosol estradiol-receptor complexes.

Pyridoxal-5'-phosphate, an inhibitor of DNA binding of glucocorticoid-, progesterone-, and estrogen-receptor complexes, also blocks the interaction of mouse uterine cytosol estradiol-receptor complexes with oligodeoxynucleotides covalently linked to celluloses. Other derivatives of pyridoxine were ineffective. The inhibition was irreversible only after borohydride reduction. Experiments with three oligodeoxynucleotides showed a 4-fold range of differences in the pyridoxal-5'-phosphate concentrations needed to inhibit 50% of the binding: oligo(dG)-cellulose, 3.1 mM; oligo(dT)-cellulose, 1.5 mM; and oligo(dC)-cellulose, 0.8 mM. Inhibition of binding occurred more rapidly with the oligodeoxypyrimidines than with oligo(dG)-cellulose. Pyridoxal-5'-phosphate was competitive with the oligodeoxynucleotides in its mode of inhibition, suggesting the polynucleotide-binding domain as a site of action. These data indicate a microheterogeneity of oligodeoxynucleotide-binding sites in the estradiol-receptor complex which is reflected in sensitivity to pyridoxal-5'-phosphate.