Two non-reactive ternary complexes of estrogenic 17 beta-hydroxysteroid dehydrogenase: crystallization and preliminary structural analysis

Human estrogenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD1, EC1.1. 1.62) is an important enzyme that catalyses the last step of active estroge n formation. 17 beta-HSDI plays a key role in the proliferation of breast c ancer cells. The three-dimensional structures of this enzyme and of the enz yme-estradiol complex have been solved (Zhu et al., 1993, J. Mol. Biol. 234 :242; Ghosh et al., 1995, Structure 3:503; Azzi et al., 1996, Nature Struct . Biol. 3.665). The determination of the non-reactive ternary complex struc ture, which could mimic the transition state, constitutes a further critica l step toward the rational design of inhibitors for this enzyme (Ghosh et a l. 1995, Structure 3:503; Penning, 1996, Endocrine-Related Cancer, 3.41). To further study the transition state, two non-reactive ternary complexes, 17 beta-HSD1-EM519-N.4DP(+) and 17 beta-HSD1-EM553-NADP(+) were crystallize d using combined methods of soaking and co-crystallization. Although they b elong to the same C2 space group, they have different unit cells, with a = 155.59 Angstrom, b = 42.82 Angstrom, c = 121.15 Angstrom, beta = 128.5 degr ees for 17 beta-HSD1-EM553-NADP(+), and a=124.01 Angstrom, b=45.16 Angstrom , c=61.40 Angstrom, beta=99.2 degrees for 17 beta-HSD1-EM553-NADP(+), respe ctively. Our preliminary results revealed that the inhibitors interact diff erently with the enzyme than do the natural substrates. (C) 1999 Elsevier S cience Ltd. All rights reserved.