Title
Testing the dependence of stabilizing effect of osmolytes on the fractional increase in the accessible surface area on thermal and chemical denaturations of proteins
Author
Safikur Rahman, Syed Ausaf Ali, Asimul Islam, Md. Imtaiyaz Hassan, Faizan Ahmad
Year
2016
Journal
Archives of Biochemistry and Biophysics
Abstract
Here we have generated two different denatured states using heat- and guanidinium chloride (GdmCl) - induced denaturations of three disulfide bond free proteins (barstar, cytochrome-c and myoglobin). We have observed that these two denatured states of barstar and myoglobin are structurally and energetically different, for, heat-induced denatured state contains many un-melted residual structure that has a significant amount of secondary and tertiary interactions. We show that structural properties of the denatured state determine the magnitude of the protein stabilization in terms of Gibbs free energy change (ΔGD°) induced by an osmolyte, i.e., the greater the exposed surface area, the greater is the stabilization. Furthermore, we predicted the m-values (ability of osmolyte to fold or unfold proteins) using Tanford's transfer-free energy model for the transfer of proteins to osmolyte solutions. We observed that, for each protein, m-value is comparable with our experimental data in cases of TMAO (trimethylamine-N-oxide) and sarcosine. However, a significant discrepancy between predicted and experimental m-values were observed in the case of glycine-betaine.
Instrument
J-1500
Keywords
Circular dichroism, Secondary structure, Thermal stability, Protein denaturation, Chemical stability, Thermodynamics, Biochemistry