Amyloid-like Fibril Formation in an All β-Barrel Protein

Acidic fibroblast growth factor from newt ( Notopthalmus viridescens ) is a ∼15-kDa, all β-sheet protein devoid of disulfide bonds. In the present study, we investigate the effects of 2,2,2-trifluoroethanol (TFE) on the structure of newt acidic fibroblast growth factor (nFGF-1). The protein aggre...

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Published in:The Journal of biological chemistry 2003-05, Vol.278 (20), p.17701
Main Authors: Sampath Srisailam, Thallampuranam Krishnaswamy S. Kumar, Dakshinamurthy Rajalingam, Karuppanan Muthusamy Kathir, Hwo-Shuenn Sheu, Fuh-Jyh Jan, Pei-Chi Chao, Chin Yu
Format: Article
Language:English
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Summary:Acidic fibroblast growth factor from newt ( Notopthalmus viridescens ) is a ∼15-kDa, all β-sheet protein devoid of disulfide bonds. In the present study, we investigate the effects of 2,2,2-trifluoroethanol (TFE) on the structure of newt acidic fibroblast growth factor (nFGF-1). The protein aggregates maximally in 10% (v/v) TFE. Congo red and thioflavin T binding experiments suggest that the aggregates induced by TFE have properties resembling the amyloid fibrils. Transmission electron microscopy and x-ray fiber diffraction data show that the fibrils (induced by TFE) are straight, unbranched, and have a cross-β structure with an average diameter of 10–15 Å. Preformed fibrils (induced by TFE) of nFGF-1 are observed to seed amyloid-like fibril formation in solutions containing the protein (nFGF-1) in the native β-barrel conformation. Fluorescence, far-UV CD, anilino-8-napthalene sulfonate binding, multidimensional NMR, and Fourier transformed infrared spectroscopy data reveal that formation of a partially structured intermediate state(s) precedes the onset of the fibrillation process. The native β-barrel structure of nFGF-1 appears to be disrupted in the partially structured intermediate state(s). The protein in the partially structured intermediate state(s) is found to be “sticky” with a solvent-exposed non-polar surface(s). Amyloid fibril formation appears to occur due to coalescence of the protein in the partially structured intermediate state(s) through solvent-exposed non-polar surfaces and intermolecular β-sheet formation among the extended, linear β-strands in the protein.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M300336200