ABSTRACT

The characteristic actions of each steroid hormone are known to be contingent on the high-affinity binding of the steroid to specific receptor proteins in the target tissues. Furthermore, hormonal function is modulated by interaction of the steroids with synthesizing and metabolizing enzymes as well as binding proteins in the blood and some specific tissues. Ultimately, X-ray analysis of the receptors, binding and transport proteins, and enzymes involved in the synthesis and metabolism of steroids and the complexes of these proteins with steroids will be required to test proposed models and mechanisms and permit truly rational drug design. A number of steroid hormones including progestins and corticoids have a two-carbon keto side chain. Examination of the structures of compounds having high affinity for estrogen, progestin, and corticoid receptors suggests that receptor binding is primarily the result of a tight association between the receptor and the steroidal A ring.