title: Molten globule state of human placental cystatin (HPC) at low pH conditions and the effects of trifluoroethanol (TFE) and methanol.
abstract: Acid-induced conformational changes were studied in human placental cystatin (HPC) in terms of circular dichroism (CD) spectroscopy, the binding of hydrophobic dye 1-anilinonapthalene-8-sulphonic acid (ANS), and intrinsic fluorescence measurements. Our results show the formation of an acid-induced molten globule state at pH 2.0, with significant secondary and tertiary interactions that resemble the native state, exposed hydrophobic regions and the effects of trifluoroethanol (TFE) and methanol in conversion of the acid-denatured state of HPC to the alcohol-induced state, which is characterized by increased helical content, disrupted tertiary structure, and the absence of hydrophobic clusters. Alcohol-induced formation of alpha-helical structures at pH 2.0 is evident from the increase in the ellipticity values at 222 nm, with native-like secondary structural features at 40% TFE. The increase in helical content was observed up to 80% TFE concentration. The ability of TFE (40%) to refold acid-denatured HPC to native-state conformation is also supported by intrinsic and ANS fluorescence measurements.
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, India.
authors.forename: Fouzia
authors.initials: F
authors.lastname: Rashid
authors.forename: Sandeep
authors.initials: S
authors.lastname: Sharma
authors.forename: M A
authors.initials: MA
authors.lastname: Baig
authors.forename: Bilqees
authors.initials: B
authors.lastname: Bano
mesh_terms: D000817:Anilino Naphthalenesulfonates; D002942:Circular Dichroism; D015891:Cystatins / Q000737:chemistry*; D005260:Female; D005456:Fluorescent Dyes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D000432:Methanol / Q000494:pharmacology; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D014270:Trifluoroethanol / Q000494:pharmacology
chemical_list: D000817:Anilino Naphthalenesulfonates; D015891:Cystatins; D005456:Fluorescent Dyes; C027132:1-anilino-8-naphthalenesulfonate; D014270:Trifluoroethanol; D000432:Methanol