Structurally homologous all beta-barrel proteins adopt different mechanisms of folding
by Srimathi, T.; Kumar, T. K. S.; Kathir, K. M.; Chi, Y. H.; Srisailam, S.; Lin, W. Y.; Chiu, I. M.; Yu, C.
Acidic fibroblast growth factors from human (hFGF-1) and newt (nFGF-1) (Notopthalamus viridescens) are 16-kDa, all beta-sheet proteins with nearly identical three-dimensional structures. Guanidine hydrochloride (GdnHCl)-induced unfolding of hFGF-1 and nFGF-1 monitored by fluorescence and far-UV circular dichroism (CD) shows that the FGF-1 isoforms differ significantly in their thermodynamic stabilities. GdnHCl-induced unfolding of nFGF-1 follows a two-state (Native state to Denatured state(s)) mechanism without detectable intermediate(s). By contrast, unfolding of hFGF-1 monitored by fluorescence, far-UV circular dichroism, size-exclusion chromatography, and NMR spectroscopy shows that the unfolding process is noncooperative and proceeds with the accumulation of stable intermediate(s) at 0.96 M GdnHCl. The intermediate (in hFGF-1) populated maximally at 0.96 M GdnHCl has molten globule-like properties and shows strong binding affinity to the hydrophobic dye, 1-Anilino-8-naphthalene sulfonate (ANS). Refolding kinetics of hFGF-1 and nFGF-1 monitored by stopped-flow fluorescence reveal that hFGF-1 and nFGF-1 adopts different folding mechanisms. The observed differences in the folding/ unfolding mechanisms of nFGF-1 and hFGF-1 are proposed to be either due to differential stabilizing effects of the charged denaturant (Gdn(+) Cl-) on the intermediate state(s) and/or due to differences in the structural interactions stabilizing the native conformation(s) of the FGF-1 isoforms.
- Journal
- Biophysical Journal
- Volume
- 85
- Issue
- 1
- Year
- 2003
- Start Page
- 459-472
- URL
- https://dx.doi.org/10.1016/s0006-3495(03)74491-9
- ISBN/ISSN
- 1542-0086; 0006-3495
- DOI
- 10.1016/s0006-3495(03)74491-9