Characterization of a partially folded intermediate of papain induced by fluorinated alcohols at low pH
Autor: | Rizwan Hasan Khan, Khursid A. Khan, Aabgeena Naeem |
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Rok vydání: | 2004 |
Předmět: |
Protein Denaturation
Protein Folding Circular dichroism Hot Temperature Protein Conformation Ultraviolet Rays Biophysics Biochemistry Anilino Naphthalenesulfonates chemistry.chemical_compound Papain Native state Guanidine Molecular Biology Protein secondary structure Fluorescent Dyes Aqueous solution Carica Chemistry Circular Dichroism Temperature Tryptophan Trifluoroethanol Hydrogen-Ion Concentration Molten globule Protein Structure Tertiary Crystallography Spectrometry Fluorescence Spectrophotometry Alcohols Protein Binding |
Zdroj: | Archives of Biochemistry and Biophysics. 432:79-87 |
ISSN: | 0003-9861 |
DOI: | 10.1016/j.abb.2004.08.019 |
Popis: | A systematic investigation of the effects of aqueous 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE) on the structure of acid-unfolded papain (EC. 3.4.22.2) was made using circular dichroism (CD), intrinsic tryptophan fluorescence, and 1-anilino 8-sulfonic acid (ANS) binding. At pH 2, papain exhibits substantial secondary structure as β-sheet and is relatively less denatured as compared to 6 M guanidine hydrochloride (GdnHCl) but loses the persistent tertiary structure of the native state. Addition of HFIP and TFE caused an induction of α-helical structure as evident from the increase in the mean residue ellipticity value at 208 and 222 nm. Induction was 20% more in HFIP than TFE. Interestingly, at 13% (v/v) HFIP and 30% (v/v) TFE a near-UV CD spectrum approaches the native-like spectral features. Tryptophan fluorescence studies indicate the change in the environment of the tryptophan residues on the addition of HFIP and TFE to acid-unfolded papain. Maximum ANS binding occurs at 13% (v/v) HFIP and 30% (v/v) TFE, suggesting a compact “molten globule”-like conformation with enhanced exposure of hydrophobic surface area. Acid-unfolded papain in presence of 13% (v/v) HFIP and 30% (v/v) TFE showed the recovery of enzymatic activity by 54 and 61%, respectively. Thermal stability of these states was assessed by changes in fluorescence emission maximum and absorbance at 292 nm. Temperature-induced unfolding of papain at pH 2 was non-cooperative and the transition curves were biphasic in nature. Temperature-induced unfolding of HFIP and TFE-induced state was weakly cooperative in comparison to cooperative transition of native. |
Databáze: | OpenAIRE |
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