Amyloidogenic potential of α-chymotrypsin in different conformational states

• Published in: Biopolymers 2009-01, Vol.91 (1), p.28-36
• Main Authors: Rezaei-Ghaleh, Nasrollah, Zweckstetter, Markus, Morshedi, Dina, Ebrahim-Habibi, Azadeh, Nemat-Gorgani, Mohsen
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amyloid - chemistry; Amyloid - metabolism; amyloid-like fibril; Animals; Cattle; Chymotrypsin - chemistry; Chymotrypsin - metabolism; Chymotrypsin - ultrastructure; Circular Dichroism; Hot Temperature; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Microscopy, Electron, Transmission; Models, Molecular; Molecular Sequence Data; protein aggregation; Protein Structure, Secondary - drug effects; Protein Structure, Tertiary - drug effects; Spectrometry, Fluorescence; trifluoroethanol; Trifluoroethanol - pharmacology; α-chymotrypsin
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.21079

Amyloid fibril formation is widely believed to be a generic property of polypeptide chains. In the present study, α‐chymotrypsin, a well‐known serine protease has been driven toward these structures by the use of two different conditions involving (I) high temperature, pH 2.5, and (II) low concentration of trifluoroethanol (TFE), pH 2.5. A variety of experimental methods, including fluorescence emission, dynamic quenching, steady‐state fluorescence anisotropy, far‐UV circular dichroism, nuclear magnetic resonance spectroscopy, and dynamic light scattering were employed to characterize the conformational states of α‐chymotrypsin that precede formation of amyloid fibrils. The structure formed under Condition I was an unfolded monomer, whereas an α‐helical rich oligomer was induced in Condition II. Both the amyloid aggregation‐prone species manifested a higher solvent exposure of hydrophobic and aromatic residues compared with the native state. Upon incubation of the protein in these conditions for 48 h, amyloid‐like fibrils were formed with diameters of about 10–12 nm. In contrast, at neutral pH and low concentration of TFE, a significant degree of amorphous aggregation was observed, suggesting that charge neutralization of acidic residues in the amyloid core region has a positive influence on amyloid fibril formation. In summary, results presented in this communication suggest that amyloid fibrils of α‐chymotrypsin may be obtained from a variety of structurally distinct conformational ensembles highlighting the critical importance of protein evolution mechanisms related to prevention of protein misfolding. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 28–36, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at [e-mail]