Heat and cold denatured states of monomeric lambda repressor are thermodynamically and conformationally equivalent.

Published

Journal Article

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.

Full Text

Duke Authors

Cited Authors

  • Huang, GS; Oas, TG

Published Date

  • May 21, 1996

Published In

Volume / Issue

  • 35 / 20

Start / End Page

  • 6173 - 6180

PubMed ID

  • 8639557

Pubmed Central ID

  • 8639557

International Standard Serial Number (ISSN)

  • 0006-2960

Digital Object Identifier (DOI)

  • 10.1021/bi960250l

Language

  • eng

Conference Location

  • United States