TAILIEUCHUNG - Báo cáo khoa học: Conformational stability of 17b-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus

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 struc-tural changes in 17b-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus(17b-HSDcl) induced by pH, temperature, salt, urea, guanidine hydrochloride, and coenzyme NADPH binding. | ỊFEBS Journal Conformational stability of 17p-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus Natasa Poklar Ulrih1 and Tea Lanisnik Rizner2 1 Department of Food Science and Technology University of Ljubljana Slovenia 2 Institute of Biochemistry University of Ljubljana Slovenia Keywords 17p-hydroxysteroid dehydrogenase coenzyme NADPH binding guanidine hydrochloride pH stability urea Correspondence N. Poklar Ulrih Department of Food Science and Technology BiotechnicalFaculty University of Ljubljana Jamnikarjeva 101 1000 Ljubljana Slovenia Fax 386 1 256 6298 Tel. 386 1 423 1161 E-mail Received 17 May 2006 revised 20 June 2006 accepted 26 June 2006 doi 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 17P-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus 17P-HSDcl induced by pH temperature salt urea guanidine hydrochloride and coenzyme NADPH binding. At 25 C and within the relatively narrow pH range of 17P-HSDcl exists in its native conformation as a dimer. This native conformation is thermally stable up to 40 C in this pH range. At 25 C and pH in the presence of 150-300 mM NaCl 17P-HSDcl forms soluble aggregates enriched in a-heli-cal and P-sheet structures. At higher temperatures and NaCl concentrations these soluble aggregates start to precipitate. The denaturants urea and guanidine hydrochloride unfold 17P-HSDcl at concentrations of and M respectively. Binding of the coenzyme NADPH to 17P-HSDcl causes local structural changes that do not significantly affect the thermal stability of this protein. Proteins of the short-chain dehydrogenase reductase SDR superfamily are nonmetallo enzymes with molecular masses between 25 and 35 kDa that function as dimers or .

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