Article

Amyloid fibril formation by a partially structured intermediate state of alpha-chymotrypsin.

Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain.
Journal of Molecular Biology (impact factor: 4). 10/2004; 342(1):321-31. DOI:10.1016/j.jmb.2004.06.089 pp.321-31
Source: PubMed

ABSTRACT Here we investigated the effects of 2,2,2-trifluoroethanol (TFE) on the structure of alpha-chymotrypsin. The protein aggregates maximally in 35% (v/v) TFE. Congo red and thioflavin-T binding experiments suggest that the aggregates induced by TFE have amyloid-like properties, and transmission electron microscopy data show that these aggregates have a fibrilar morphology. Fluorescence, circular dichroism, anilino-8-napthalene sulfonate binding, and Fourier-transformed infrared spectroscopy data suggest that formation of a partially structured intermediate state precedes the onset of the aggregation process. The native beta-barrel structure of alpha-chymotrypsin appears to be disrupted in the partially structured intermediate state in favour of a non-native extended beta-sheet conformation with exposed hydrophobic surfaces. The protein becomes "sticky" under these conditions and aggregates into amyloid-like structures. The data support the hypothesis that amyloid formation involves the ordered self-assembly of partially folded species that are critical soluble precursors of fibrilar aggregates.

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Keywords

aggregates
 
aggregates induced
 
aggregation process
 
amyloid formation
 
amyloid-like structures
 
beta-sheet conformation
 
Congo red
 
critical soluble precursors
 
data support
 
fibrilar aggregates
 
Fluorescence
 
Fourier-transformed infrared spectroscopy data
 
hydrophobic surfaces
 
native beta-barrel structure
 
ordered self-assembly
 
protein aggregates maximally
 
structured intermediate state
 
structured intermediate state precedes
 
TFE
 
transmission electron microscopy data