Crystallization and preliminary crystal structure of the complex of 17beta-hydroxysteroid dehydrogenase with a dual-site inhibitor

Human estrogenic 17β-hydroxysteroid dehydrogenase (17β-HSD1) catalyzes the synthesis of 17β-estradiol (E₂) from estrone, in the ovary and peripheral tissues. While the structures of 17β-HSD1 alone and in complex with E₂ have been determined (D. Ghosh, V. Pletnev, D.-W. Zhu, Z. Wawrzak, W.-L. Duax, W. Pangborn, F. Labrie, S.-X. Lin, Structure of human 17β-hydroxysteroid dehydrogenase at 2.20 Å resolution, Structure 3 (1995) 503–513; A. Azzi, P.H. Rhese, D.-W. Zhu, R.L. Campbell, F. Labrie, S.-X. Lin, Crystal structure of human estrogenic 17β-hydroxysteroid dehydrogenase complexed with 17_β-estradiol, Nature Struct. Biol. 3 (1996) 665–668, no structures of inhibitor/enzyme complex, either modeled or from crystallography, have been reported before the submission of the present paper. The best available inhibitors are among the ‘dual-site inhibitors’, blocking estrogenic 17β-HSD and the estrogen receptor. These compounds belong to a family of estradiol analogues having an halogen atom at the 16 position and an extended alkyl-amide chain at the 7 position (C. Labrie, G. Martel, J.M. Dufour, G. Levesque, Y. Merand, F. Labrie, Novel compounds inhibit estrogen formation and action, Cancer Res. 52 (1992) 610–615). We now report the crystallization of this enzyme/inhibitor complex. The complex of the best available dual-site inhibitor, EM-139, with 17β-HSD1 has been crystallized using both cocrystallization and soaking methods. Crystals are isomorphous to the native crystals grown in the presence of 0.06% β-octyl-glucoside and polyethyleneglycol 4000, with a monoclinic space group C2. Data at 1.8 Å have been collected from a synchrotron source. Even though the size of the inhibitor is greater than that of the substrate, our preliminary X-ray-diffraction study shows that EM-139 fits into the active site in a position similar to that of estrogen. The availability of such structural data will help design more potent inhibitors of estrogenic 17β-HSD.