Inhibition of the binding of dexamethasone to mammary cytoplasmic glucocorticoid receptor by phenylglyoxal.

We have studied the effects of phenylglyoxal and other related arginine-specific reagents on the mammary cytoplasmic glucocorticoid receptor. Our studies show that phenylglyoxal can inhibit the binding of [3H]dexamethasone to the steroid-free receptor and also displace the bound [3H]dexamethasone from the steroid-receptor complex. The kinetics of the binding reaction reveals that the inhibition of phenylglyoxal may be due to its ability to interact with the steroid binding site of the receptor. Similar data are also obtained with other arginine-modifying agents such as 1,2-cyclohexanedione. Thus, these studies suggest that arginine residues may be involved in the binding of glucocorticoids to mammary cytoplasmic glucocorticoid receptor.