Human 17 beta-hydroxysteroid dehydrogenase-ligand complexes: crystals of different space groups with various cations and combined seeding and co-crystallization

Human estrogenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD1) is res ponsible for the synthesis of active estrogens that stimulate the prolifera tion of breast cancer cells. The enzyme has been crystallized using a Mg2+/ PEG (3500)/beta-octyl glucoside system [Zhu et al., J. Mel. Biol. 234 (1993 ) 242]. The space group of these crystals is C2. Here we report that cation s can affect 17 beta-HSD1 crystallization significantly. In the presence of Mn2+ instead of Mg2+, crystals have been obtained in the same space group with similar unit cell dimensions. In the presence of Li+ and Na+ instead o f Mg2+, the space group has been changed to P2(1)2(1)2(1). A whole data set for a crystal of 17 beta-HSD1 complex with progesterone grown in the prese nce of Li+ has been collected to 1.95 Angstrom resolution with a synchrotro n source. The cell dimensions are a = 41.91 Angstrom, b = 108.21 Angstrom, c = 117.00 Angstrom. The structure has been preliminarily determined by mol ecular replacement, yielding important information on crystal packing in th e presence of different cations. In order to further understand the structu re-function relationship of 17 beta-HSD1, enzyme complexes with several lig ands have been crystallized. As the steroids have very low aqueous solubili ty, we used a combined method of seeding and co-crystallization to obtain c rystals of 17 beta-HSD1 complexed with various ligands. This method provide s ideal conditions for growing complex crystals, with ligands such as 20 al pha-hydroxysteroid progesterone, testosterone and 17 beta-methyl-estradiol- NADP(+). Several complex structures have been determined with reliable elec tronic density of the bound ligands. (C) 1999 Elsevier Science B.V. All rig hts reserved.