# Linear free-energy model description of the conformational stability of uracil-DNA glycosylase inhibitor

Reddy, Bhanuprakash G and Purnapatre, Kedar and Lawrence, Rajendran and Roy, Sudipta and Varshney, Umesh and Surolia, Avadhesha (1999) Linear free-energy model description of the conformational stability of uracil-DNA glycosylase inhibitor. In: European Journal of Biochemistry, 261 (3). pp. 610-617.

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## Abstract

The equilibrium unfolding of uracil DNA glycosylase inhibitor (Ugi), a small acidic protein of molecular mass 9474 Da, has been studied by a combination of thermal-induced and guanidine hydrochloride (GdnCl)-induced denaturation. The analysis of the denaturation data provides a measure of the changes in conformational free energy, enthalpy, entropy and heat capacity $\Delta\hspace{2mm}C_p$ that accompany the equilibrium unfolding of Ugi over a wide range of temperature and GdnCl concentration. The unfolding of Ugi is a simple two-state, reversible process. The protein undergoes both low-temperature and high-temperature unfolding even in the absence of GdnCl but more so in the presence of denaturant. The data are consistent with the linear free-energy model and with a temperature independent $\Delta\hspace{2mm}C_p$ over the large temperature range of unfolding. The small $\Delta\hspace{2mm}C_p$ $(6.52 kJ•mol^{-1}K^{-1})$ for the unfolding of Ugi, is perhaps a reflection of a relatively small, buried hydrophobic core in the folded form of this small monomeric protein. Despite a relatively low value of $\Delta\hspace{2mm}G_{(H2O)}$, 7.40 kJ•$mol^-1$ at pH 8.3, Ugi displays considerable stability with the temperature of maximum stability being 301.6 K.

Item Type: Journal Article Copyright of this article belongs to FEBS. Cold denaturation;Heat capacity change;Linear free-energy model;Protein stability;Uracil-DNA glycosylase inhibitor. Division of Biological Sciences > Molecular Biophysics UnitDivision of Biological Sciences > Microbiology & Cell Biology 16 Oct 2007 19 Sep 2010 04:40 http://eprints.iisc.ernet.in/id/eprint/12074