title: Trifluoroethanol increases the stability of Delta(5)-3-ketosteroid isomerase. 15N NMR relaxation studies.
abstract: In the equilibrium unfolding process of Delta(5)-3-ketosteroid isomerase from Pseudomonas testosteroni by urea, it was observed that the enzyme stability increases by 2.5 kcal/mol in the presence of 5% trifluoroethanol (TFE). To elucidate the increased enzyme stability by TFE, the backbone dynamics of Delta(5)-3-ketosteroid isomerase were studied in the presence and absence of 5% TFE by (15)N NMR relaxation measurements, and the motional parameters (S(2), tau(e), and R(ex)) were extracted from the relaxation data using the model-free formalism. The presence of 5% TFE causes little change or a slight increase in the order parameters (S(2)) for a number of residues, which are located mainly in the dimer interface region. However, the majority of the residues exhibit reduced order parameters in the presence of 5% TFE, indicating that high frequency (pico- to nanosecond) motions are generally enhanced by TFE. The results suggest that the entropy can be an important factor for the enzyme stability, and the increase in entropy by TFE is partially responsible for the increased stability of Delta(5)-3-ketosteroid isomerase.
authors.affiliation: Department of Chemistry, Pohang University of Science and Technology, Pohang, 790-784, Korea.
authors.forename: Sunggoo
authors.initials: S
authors.lastname: Yun
authors.forename: Do Soo
authors.initials: DS
authors.lastname: Jang
authors.forename: Gildon
authors.initials: G
authors.lastname: Choi
authors.forename: Kwang S
authors.initials: KS
authors.lastname: Kim
authors.forename: Kwan Yong
authors.initials: KY
authors.lastname: Choi
authors.forename: Hee Cheon
authors.initials: HC
authors.lastname: Lee
mesh_terms: D004058:Diffusion; D004795:Enzyme Stability; D009682:Magnetic Resonance Spectroscopy; D017510:Protein Folding; D012399:Rotation; D013251:Steroid Isomerases / Q000737:chemistry*; D014270:Trifluoroethanol / Q000494:pharmacology*; D014508:Urea / Q000494:pharmacology
chemical_list: D014270:Trifluoroethanol; D014508:Urea; D013251:Steroid Isomerases; C022660:steroid delta-isomerase