Structural events during the refolding of an all beta-sheet protein.
The refolding kinetics of the 140-residue, all beta-sheet, human fibroblast growth factor (hFGF-1) is studied using a variety of biophysical techniques such as stopped-flow fluorescence, stopped-flow circular dichroism, and quenched-flow hydrogen exchange in conjunction with multidimensional NMR spectroscopy. Urea-induced unfolding of hFGF-1 under equilibrium conditions reveals that the protein folds via a two-state (native <--> unfolded) mechanism without the accumulation of stable intermediates. However, measurement of the unfolding and refolding rates in various concentrations of urea shows that the refolding of hFGF-1 proceeds through accumulation of kinetic intermediates. Results of the quenched-flow hydrogen exchange experiments reveal that the hydrogen bonds linking the N- and C-terminal ends are the first to form during the refolding of hFGF-1. The basic beta-trefoil framework is provided by the simultaneous formation of beta-strands I, IV, IX, and X. The other beta-strands comprising the beta-barrel structure of hFGF-1 are formed relatively slowly with time constants ranging from 4 to 13 s.
Samuel
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D
Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan.
Kumar
T K
TK
Balamurugan
K
K
Lin
W Y
WY
Chin
D H
DH
Yu
C
C
D016220:Fibroblast Growth Factor 1; D016222:Fibroblast Growth Factor 2 / Q000737:chemistry*; D006801:Humans; D006859:Hydrogen / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding
D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; D006859:Hydrogen