title: Intermediate conformation between native β-sheet and non-native α-helix is a precursor of trifluoroethanol-induced aggregation of human carbonic anhydrase-II.
abstract: In the present work, we examined the correlation between 2,2,2-trifluoroethanol (TFE)-induced conformational transitions of human carbonic anhydrase II (HCAII) and its aggregation propensity. Circular dichroism data indicates that protein undergoes a transition from β-sheet to α-helix on addition of TFE. The protein was found to aggregate maximally at moderate concentration of TFE at which it exists somewhere between β-sheet and α-helix, probably in extended non-native β-sheet conformation. Thioflavin-T (ThT) and Congo-Red (CR) assays along with fluorescence microscopy and transmission electron microscopy (TEM) data suggest that the protein aggregates induced by TFE possess amyloid-like features. Anilino-8-naphthalene sulfonate (ANS) binding studies reveal that the exposure of hydrophobic surface(s) was maximum in intermediate conformation. Our study suggests that the exposed hydrophobic surface and/or the disruption of the structural features protecting a β-sheet protein might be the major reason(s) for the high aggregation propensity of non-native intermediate conformation of HCAII.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
authors.forename: Preeti
authors.initials: P
authors.lastname: Gupta
authors.affiliation: Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India. Electronic address: sdeep@chemistry.iitd.ac.in.
authors.forename: Shashank
authors.initials: S
authors.lastname: Deep
mesh_terms: D024402:Carbonic Anhydrase II / Q000737:chemistry*; D019281:Dimerization; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D014270:Trifluoroethanol / Q000737:chemistry*
chemical_list: D014270:Trifluoroethanol; D024402:Carbonic Anhydrase II
keywords: Amyloid fibril; Human carbonic anhydrase II; Partially structured conformation; Protein aggregation; Trifluoroethanol