Crystallization, X-ray Diffraction Analysis and Phasing of 17beta-Hydroxysteroid Dehydrogenase from fungus Cochliobolus lunatus

17-Hydroxysteroid dehydrogenase from the filamentous fungus Cochliobolus lunatus (17-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. 17-HSDcl has recently been characterized and cloned and has been the subject of several functional studies. Although several hypotheses on the physiological role of 17-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 17-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.