title: Characterization and properties of steroid binding protein in Bufo arenarum serum.
abstract: Serum steroid binding properties of mature Bufo arenarum females were studied. Binding data obtained using charcoal adsorption assay and equilibrium dialysis methods indicates a single protein, named Bufo arenarum sex binding protein (Ba SBP), which binds 5 alpha-dihydrotestosterone (DHT), testosterone (T), and estradiol-17 beta (E2) with high affinity (10(-7) M-1 - 10(8) M-1) and fair capacity (10(-6) M). Scatchard plot analysis demonstrated the coexistence of two binding sites. Ba SBP has a sedimentation coefficient of 5.2 S in sucrose gradient centrifugation in low salt and under steady-state conditions. The specificity of this protein, determined by competitive binding experiments, is comparable to human SBP. DHT and T bind with higher affinity than E2. Estriol and estrone competed poorly, while diethylstilbestrol and C21 steroids did not compete. The binding capacity of this protein is under estrogenic control.
authors.affiliation: Instituto Superior de Investigaciones Biológicas, Departamento de Biología del Dessarrollo, Tucumán, Argentina.
authors.forename: S N
authors.initials: SN
authors.lastname: Fernández
authors.forename: Z C
authors.initials: ZC
authors.lastname: Mansilla-Whitacre
authors.forename: D C
authors.initials: DC
authors.lastname: Miceli
mesh_terms: D000818:Animals; D001665:Binding Sites; D002022:Bufo arenarum / Q000097:blood*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D013196:Dihydrotestosterone / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism; D005260:Female; D010052:Ovariectomy; D011485:Protein Binding; D012738:Sex Hormone-Binding Globulin / Q000302:isolation & purification / Q000378:metabolism*; D013696:Temperature; D013739:Testosterone / Q000378:metabolism
chemical_list: D012738:Sex Hormone-Binding Globulin; D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol