title: Molten globule-like partially folded state of Bacillus licheniformis α-amylase at low pH induced by 1,1,1,3,3,3-hexafluoroisopropanol.
abstract: Effect of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) on acid-denatured Bacillus licheniformis α -amylase (BLA) at pH 2.0 was investigated by far-UV CD, intrinsic fluorescence, and ANS fluorescence measurements. Addition of increasing HFIP concentrations led to an increase in the mean residue ellipticity at 222 nm (MRE 222 nm) up to 1.5 M HFIP concentration beyond which it sloped off. A small increase in the intrinsic fluorescence and a marked increase in the ANS fluorescence were also observed up to 0.4 M HFIP concentration, both of which decreased thereafter. Far- and near-UV CD spectra of the HFIP-induced state observed at 0.4 M HFIP showed significant retention of the secondary structures closer to native BLA but a disordered tertiary structure. Increase in the ANS fluorescence intensity was also observed with the HFIP-induced state, suggesting exposure of the hydrophobic clusters to the solvent. Furthermore, thermal denaturation of HFIP-induced state showed a non-cooperative transition. Taken together, all these results suggested that HFIP-induced state of BLA represented a molten globule-like state at pH 2.0.
authors: Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors: Adyani Azizah
authors: AA
authors: Abd Halim
authors: Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia ; Faculty of Applied Medical Sciences, University of Gezira, P.O. Box 20, 2667 Wad Medani, Sudan.
authors: Mohammed Suleiman
authors: MS
authors: Zaroog
authors: Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors: Habsah Abdul
authors: HA
authors: Kadir
authors: Biomolecular Research Group, Biochemistry Programme, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors: Saad
authors: S
authors: Tayyab
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D020005:Propanols / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D000516:alpha-Amylases / Q000737:chemistry* / Q000648:ultrastructure*; D006845:Hydrocarbons, Fluorinated
chemical_list: D020005:Propanols; D000516:alpha-Amylases; C001337:hexafluoroisopropanol; D006845:Hydrocarbons, Fluorinated