Rowland S S, Falkler W A, Bashirelahi N
Department of Microbiology, University of Maryland Dental School, Baltimore 21201.
J Steroid Biochem Mol Biol. 1992 Aug;42(7):721-7. doi: 10.1016/0960-0760(92)90113-w.
A constitutive estrogen-binding protein (EBP) has been identified in the cytosol of Pseudomonas aeruginosa, a Gram-negative bacterium. All 14 strains tested contained the EBP. Estradiol binding was rapid and maximal binding occurred by 90 min at 0 degrees C. Dissociation of estradiol from the binding protein occurred at a rate of 4.6 fmol/min with a t1/2 of 42 min. EBP binding was destroyed by protease treatment and at high temperature. Sodium molybdate had no effect on binding. The Kd determined by Scatchard analysis was 3.9 nM and the Bmax was 323 fmol/mg protein. The EBP sedimented at 8.9 S on sucrose density gradients. The presence of 0.4 M KCl increased estradiol binding 6-fold but did not cause a shift in the sedimentation value. Gel filtration of the native protein gave an estimated molecular weight of 215,000 and a Stokes radius of 50.2 A. Steroid binding specificity, in order of decreasing affinity, was estradiol, estrone, dihydrotestosterone, estriol, testosterone, progesterone and promegestone. Other steroid hormones tested did not compete for estradiol binding. Identification of an EBP in a bacterium allows a comparative analysis of other steroid-binding proteins in unicellular microorganisms.
在革兰氏阴性菌铜绿假单胞菌的胞质溶胶中已鉴定出一种组成型雌激素结合蛋白（EBP）。所测试的所有14个菌株均含有EBP。雌二醇结合迅速，在0℃下90分钟时达到最大结合。雌二醇从结合蛋白上的解离速率为4.6 fmol/分钟，半衰期为42分钟。EBP结合会被蛋白酶处理和高温破坏。钼酸钠对结合没有影响。通过Scatchard分析确定的Kd为3.9 nM，Bmax为323 fmol/mg蛋白。EBP在蔗糖密度梯度上以8.9 S沉降。0.4 M KCl的存在使雌二醇结合增加了6倍，但未导致沉降值发生变化。对天然蛋白进行凝胶过滤得到的估计分子量为215,000，斯托克斯半径为50.2 Å。按亲和力递减顺序排列的类固醇结合特异性为雌二醇、雌酮、二氢睾酮、雌三醇、睾酮、孕酮和孕美雌酮。所测试的其他类固醇激素不竞争雌二醇结合。在细菌中鉴定出EBP有助于对单细胞微生物中的其他类固醇结合蛋白进行比较分析。
