Diethylpyrocarbonate, a histidine selective reagent, inhibits progestin binding to chick oviduct cytosol

In this report we describe experiments showing that diethylpyrocarbonate, a histidine selective reagent, inhibits progestin binding to the chick oviduct progesterone receptor. Because this inhibition is reversed by hydroxylamine, we suggest that the chick oviduct progesterone receptor contains one or more histidine residues that regulate progestin binding. We also find that the progestin R5020 protects the progesterone receptor from diethylpyrocarbonate mediated inhibition of progestin binding. From this we infer that the progestin binding site contains a histidine residue(s) important for progesterone binding to its receptor in chick oviduct.