Crystallization, X-ray diffraction analysis and phasing of 17beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus.

17beta-Hydroxysteroid dehydrogenase from the filamentous fungus Cochliobolus lunatus (17beta-HSDcl) is an NADP(H)-dependent enzyme that preferentially catalyses the oxidoreduction of oestrogens and androgens. The enzyme belongs to the short-chain dehydrogenase/reductase superfamily and is the only fungal hydroxysteroid dehydrogenase known to date. 17beta-HSDcl has recently been characterized and cloned and has been the subject of several functional studies. Although several hypotheses on the physiological role of 17beta-HSDcl in fungal metabolism have been formulated, its function is still unclear. An X-ray crystallographic study has been undertaken and the optimal conditions for crystallization of 17beta-HSDcl (apo form) were established, resulting in well shaped crystals that diffracted to 1.7 A resolution. The space group was identified as I4(1)22, with unit-cell parameters a = b = 67.14, c = 266.77 A. Phasing was successfully performed by Patterson search techniques. A catalytic inactive mutant Tyr167Phe was also engineered, expressed, purified and crystallized for functional and structural studies.