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Biochemical Reconstitution of Steroid Receptor•Hsp90 Protein Complexes and Reactivation of Ligand Binding
Published on: September 21, 2011
Conformational stability of 17 beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus
Natasa Poklar Ulrih1, Tea Lanisnik Rizner
1Department of Food Science and Technology, University of Ljubljana, Slovenia. natasa.poklar@bf.uni-lj.si
Abstract:
The functional activities of proteins are closely related to their molecular structure and understanding their structure-function relationships remains one of the intriguing problems of molecular biology. We investigated structural changes in 17beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17beta-HSDcl) induced by pH, temperature, salt, urea, guanidine hydrochloride, and coenzyme NADPH binding. At 25 degrees C and within the relatively narrow pH range of 7.0-9.0, 17beta-HSDcl exists in its native conformation as a dimer. This native conformation is thermally stable up to 40 degrees C in this pH range. At 25 degrees C and pH 2.0 in the presence of 150-300 mM NaCl, 17beta-HSDcl forms soluble aggregates enriched in alpha-helical and beta-sheet structures. At higher temperatures and NaCl concentrations, these soluble aggregates start to precipitate. The denaturants urea and guanidine hydrochloride unfold 17beta-HSDcl at concentrations of 1.2 and 0.4 M, respectively. Binding of the coenzyme NADPH to 17beta-HSDcl causes local structural changes that do not significantly affect the thermal stability of this protein.
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