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Conformational stability of 17β‐hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus
Author(s) -
Ulrih Nataša Poklar,
Lanišnik Rižner Tea
Publication year - 2006
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2006.05396.x
Subject(s) - guanidine , chemistry , dimer , urea , hydrochloride , crystallography , stereochemistry , biochemistry , organic chemistry
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 17β‐hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17β‐HSDcl) induced by pH, temperature, salt, urea, guanidine hydrochloride, and coenzyme NADPH binding. At 25 °C and within the relatively narrow pH range of 7.0–9.0, 17β‐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 2.0 in the presence of 150–300 m m NaCl, 17β‐HSDcl forms soluble aggregates enriched in α‐helical and β‐sheet structures. At higher temperatures and NaCl concentrations, these soluble aggregates start to precipitate. The denaturants urea and guanidine hydrochloride unfold 17β‐HSDcl at concentrations of 1.2 and 0.4 m , respectively. Binding of the coenzyme NADPH to 17β‐HSDcl causes local structural changes that do not significantly affect the thermal stability of this protein.