Purification and binding site characterization of the circulating trophoblastic androgen-binding protein.
The trophoblastic androgen-binding protein (t-ABP) was purified 150-fold with a recovery of 51% from serum of patients with hydatidiform mole using various chromatographic techniques, successively affinity on concanavalin A, ion exchange on QAE-Sephadex A 50, gel filtration on Sephadex G 200 and chromatofocusing. The chromatofocusing step eliminated any trace of contaminating sex-hormone binding globulin. Competitive binding experiments using the purified material, [3H]dihydrotestosterone and various steroid derivatives allowed an attempt at characterizing the steroid-binding site of the protein. This latter possess respectively hydrophilic domains facing position 2 and 17 of the steroid molecule, a hydrophilic and proton donor sequence facing position 3 of the steroid molecule, hydrophobic regions facing positions 6, 11 and 16 of the steroid molecule and electron donor domains facing positions 1 and 6 of the steroid molecule. These characteristics are compared with those of the sex hormone-binding globulin (SHBG), rat epididymis androgen-binding protein (RABP) and rat prostate cytoplasmic androgen receptor (CAR) binding sites, respectively. The results of this specificity study indicate that the t-ABP behaves very similarly to CAR, although major differences are likely to exist between the binding sites of both proteins, particularly in the protein domains facing C-1 and C-2 of the steroid.
D000727:Androgen-Binding Protein / Q000097:blood*; D000728:Androgens / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins; D055598:Chemical Phenomena; D002621:Chemistry; D002845:Chromatography; D013196:Dihydrotestosterone / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism; D005260:Female; D006801:Humans; D006828:Hydatidiform Mole / Q000097:blood*; D011247:Pregnancy; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014594:Uterine Neoplasms / Q000097:blood*
D000727:Androgen-Binding Protein; D000728:Androgens; D002352:Carrier Proteins; D004967:Estrogens; C051188:trophoblastic androgen-binding protein, human; D013196:Dihydrotestosterone