title: Conformational stability of 17 beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus.
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.
authors.affiliation: Department of Food Science and Technology, University of Ljubljana, Slovenia. natasa.poklar@bf.uni-lj.si
authors.forename: Natasa Poklar
authors.initials: NP
authors.lastname: Ulrih
authors.forename: Tea
authors.initials: T
authors.lastname: Lanisnik Rizner
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000737:chemistry* / Q000378:metabolism*; D001203:Ascomycota / Q000201:enzymology*; D002942:Circular Dichroism; D004795:Enzyme Stability; D019791:Guanidine; D006863:Hydrogen-Ion Concentration; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014508:Urea
chemical_list: D011994:Recombinant Proteins; D014508:Urea; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase; D019791:Guanidine