Amyloid-like fibril formation in an all beta-barrel protein. Partially structured intermediate state(s) is a precursor for fibril formation.
Acidic fibroblast growth factor from newt (Notopthalmus viridescens) is a approximately 15-kDa, all beta-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-beta structure with an average diameter of 10-15 A. 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 beta-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 beta-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 beta-sheet formation among the extended, linear beta-strands in the protein.
Srisailam
Sampath
S
Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan.
Kumar
Thallampuranam Krishnaswamy S
TK
Rajalingam
Dakshinamurthy
D
Kathir
Karuppanan Muthusamy
KM
Sheu
Hwo-Shuenn
HS
Jan
Fuh-Jyh
FJ
Chao
Pei-Chi
PC
Yu
Chin
C
D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism*; D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D000818:Animals; D052160:Benzothiazoles; D002942:Circular Dichroism; D003224:Congo Red / Q000494:pharmacology; D016220:Fibroblast Growth Factor 1 / Q000737:chemistry* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology; D007554:Isotopes; D009682:Magnetic Resonance Spectroscopy; D008854:Microscopy, Electron; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D012455:Salamandridae; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D014466:Ultraviolet Rays; D014961:X-Ray Diffraction
D016229:Amyloid beta-Peptides; D000817:Anilino Naphthalenesulfonates; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D007554:Isotopes; D011994:Recombinant Proteins; D013844:Thiazoles; D016220:Fibroblast Growth Factor 1; C009462:thioflavin T; D003224:Congo Red; C027132:1-anilino-8-naphthalenesulfonate