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

Human estrogenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD1) cataly zes the synthesis of 17 beta-estradiol (E-2) from estrone, in the ovary and peripheral tissues. While the structures of 17 beta-HSD1 alone and in comp lex with E-2 have been determined (D. Ghosh, V. Pletnev, D.-W. Zhu, Z. Wawr zak, W.-L. Duax, W. Pangborn, F. Labrie, S.-X. Lin, Structure of human 17 b eta-hydroxysteroid dehydrogenase at 2.20 Angstrom resolution, Structure 3 ( 1995) 503-513), no structures of inhibitor/enzyme complex, either modeled o r from crystallography, have been reported before the submission of the pre sent paper. The best available inhibitors are among the 'dual-site inhibito rs', blocking estrogenic 17 beta-HSD and the estrogen receptor. These compo unds belong to a family of estradiol analogues having an halogen atom at th e 16 alpha position and an extended alkyl-amide chain at the 7 alpha positi on (C. Labrie, G. Martel, J.M. Dufour, G. Levesque, Y. Merand, F. Labrie, N ovel compounds inhibit estrogen formation and action, Cancer Res. 52 (1992) 610-615). We now report the crystallization of this enzyme/inhibitor compl ex. The complex of the best available dual-site inhibitor, EM-139, with 17 beta-HSD1 has been crystallized using both cocrystallization and soaking me thods. Crystals are isomorphous to the native crystals grown in the presenc e of 0.06% beta-octyl-glucoside and polyethyleneglycol 4000, with a monocli nic space group C2. Data at 1.8 Angstrom have been collected from a synchro tron 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 fi ts into the active site in a position similar to that of estrogen. The avai lability of such structural data will help design more potent inhibitors of estrogenic 17 beta-HSD. (C) 1999 Elsevier Science Ltd. All rights reserved .