title: Testosterone-estradiol binding globulin binds to 2-methoxyestradiol with greater affinity than to testosterone.
abstract: This report describes the unexpected observation that testosterone-estradiol binding globulin (TeBG) binds 2-methoxyestradiol better than it binds either testosterone or 17 beta-estradiol. As determined by competitive displacement of 3H-testosterone from TeBG adsorbed onto a solid phase matrix of Con A-Sepharose, the relative binding activities of 2-methoxyestradiol, testosterone and 17 beta-estradiol for TeBG were 2.0, 1.0 and 0.32, respectively. In contrast, 2-methoxyestradiol, which is known to bind with low affinity to estrogen receptors, had only low affinity binding to the androgen receptor, as determined by competitive displacement of 3H-dihydrotestosterone using 64-24 rat mammary tumor cells. 2-Methoxyestradiol is the first example of a naturally occurring steroid which binds with high affinity to TeBG but with low affinity to both androgen and estrogen receptors.
mesh_terms: D000077584:2-Methoxyestradiol; D001667:Binding, Competitive; D004958:Estradiol / Q000031:analogs & derivatives*; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D011944:Receptors, Androgen / Q000378:metabolism; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013739:Testosterone
chemical_list: D011944:Receptors, Androgen; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone; D004958:Estradiol; D000077584:2-Methoxyestradiol