Abstract

PIP: The binding potential of 41 different steroids to reduced rabbit ute roglobulin, in competition with progesterone, was assessed to determine the molecular structural requirements for interaction with the receptor site of uteroglobulin. Estradiol-17beta and testosterone bound to the same site as progesterone, but with lower affinity. Uteroglobulin showed a hydrophobic interaction with the alpha-side of progesterone. The active site of uteroglobulin seems capable of receiving various configurations of the A-ring and side chain, including the phenolic A-ring of estrogens and the C-17alpha-ethinyl side chain of some synthetic steroids, particularly norethynodrel. Except for estrogens, the potential of various steroids to bind to uteroglobulin correlated well with their progestational activity.