Orstan A, Lulka M F, Eide B, Petra P H, Ross J B
Biochemistry. 1986 May 6;25(9):2686-92. doi: 10.1021/bi00357a060.
The interaction of the estrogen d-3-hydroxy-1,3,5(10),6,8-estrapentaen-17-one (equilenin) with the human and rabbit sex steroid binding proteins (hSBP and rSBP, respectively) has been investigated by using fluorescence and absorption spectroscopy. Equilenin competes for the binding of 5 alpha-dihydrotestosterone. The calculated binding constant of equilenin for rSBP is 1.9 X 10(7) M-1 at 4 degrees C, which can be compared with the binding constant of 5.7 X 10(7) M-1 reported for hSBP [Ross, J.B.A., Torres, R., & Petra, P.H. (1982) FEBS Lett. 149, 240]. The results of fluorescence quenching experiments with the collisional quenchers KI and acrylamide indicate that the bound steroid has limited accessibility to the bulk solvent and that there are no anionic surface groups near the steroid-binding site. The fluorescence excitation spectra of SBP-equilenin complexes are similar to the absorption spectra of equilenin in low-dielectric solvents. The fluorescence emission of the SBP-equilenin complexes, however, exhibits wavelength shifts (red shifts) opposite to those of the steroid in low-dielectric solvents or complexed with beta-cyclodextrin (blue shifts) but similar to the red shift produced by addition of the proton acceptor triethylamine to equilenin in cyclohexane. These data indicate that the steroid-binding site of hSBP and rSBP is a nonpolar cavity containing a proton acceptor that participates in a specific interaction, possibly a hydrogen bond, with the 3'-hydroxyl group of the bound steroid.
通过荧光光谱和吸收光谱法研究了雌激素d-3-羟基-1,3,5(10),6,8-雌甾五烯-17-酮（马萘雌酮）与人及兔性类固醇结合蛋白（分别为hSBP和rSBP）的相互作用。马萘雌酮竞争5α-二氢睾酮的结合。在4℃下，计算得出马萘雌酮与rSBP的结合常数为1.9×10⁷ M⁻¹，可与报道的hSBP的结合常数5.7×10⁷ M⁻¹进行比较[罗斯，J.B.A.，托雷斯，R.，&佩特拉，P.H.（1982年）《欧洲生物化学学会联合会快报》149, 240]。用碰撞猝灭剂碘化钾和丙烯酰胺进行的荧光猝灭实验结果表明，结合的类固醇与本体溶剂的可及性有限，且类固醇结合位点附近没有阴离子表面基团。SBP-马萘雌酮复合物的荧光激发光谱与马萘雌酮在低介电常数溶剂中的吸收光谱相似。然而，SBP-马萘雌酮复合物的荧光发射表现出与低介电常数溶剂中类固醇或与β-环糊精络合时相反的波长位移（红移），但与在环己烷中向马萘雌酮中加入质子受体三乙胺所产生的红移相似。这些数据表明，hSBP和rSBP的类固醇结合位点是一个非极性腔，其中含有一个质子受体，该受体与结合类固醇的3'-羟基参与特定相互作用，可能是氢键。
