Although the denaturation of proteins by low temperatures is a well-documented phenomenon, little is known about the molecular details of the process. In this study, the parameters describing the denaturation thermodynamics of residues 6-85 of the N-terminal domain of lambda repressor have been determined by fitting the three-dimensional thermal-urea denaturation surface obtained by circular dichroism. The shape of the surface shows cold denaturation at low temperatures and urea concentrations above 2 M, which allows accurate determination of the apparent heat capacity of denaturation (delta Cp). Denaturation curves based on aromatic 1H NMR spectra give identical denaturation curves, confirming purely twostate folding under all conditions studies. The denaturation surface can be fit with constant delta Cp and delta In KD/delta[urea] (KD is the equilibrium constant for denaturation), consistent with a thermodynamically invariant denatured state. In addition, the aromatic 1H NMR spectrum of the cold denatured state at 0 degree C in 3 M uea is essentially identical to the spectrum at 70 degree C in 3 M urea. These observations indicate that the structures of the cold and heat denatured states, in the presence of 3 M urea, are thermodynamically and conformationally equivalent. Study holds ProTherm entries: 5029, 5030, 5031, 5032 Extra Details: aromatic 1H NMR spectra; denaturation curves; twostate folding;,conformationally equivalent
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:28 p.m.
|Number of data points||5|
|Proteins||Repressor protein cI ; Repressor protein cI|
|Assays/Quantities/Protocols||Experimental Assay: dG_H2O temp:37.0 C ; Experimental Assay: dG_H2O temp:25.0 C ; Experimental Assay: dG_H2O temp:13.0 C ; Experimental Assay: Tm ; Experimental Assay: dHvH|
|Libraries||Mutations for sequence STKKKPLTQEQLEDARRLKAIYEKKKNELGLSQESVADKMGMGQSGVGALFNGINALNAYNAALLAKILKVSVEEFSPSIAREIYEMYEAVS|