Journal of the American Chemical Society, Vol.135, No.50, 18884-18891, 2013
The Mechanism of Denaturation and the Unfolded State of the alpha-Helical Membrane-Associated Protein Mistic
In vitro protein-folding studies using chemical denaturants such as urea are indispensible in elucidating the forces and mechanisms determining the stability, structure, and dynamics of water-soluble proteins. By contrast, a-helical membrane-associated proteins largely evade such approaches because they are resilient to extensive unfolding We have used of the alpha-helical membrane-associated protein Mistic as well as dissection of the effects of urea on the structure and dynamics optical and NMR spectroscopy to provide an atomistic-level its interactions with detergent and solvent molecules. In the presence of the zwitterionic detergent lauryl dimethylamine oxide, increasing concentrations of urea result in a complex sequence of conformational changes that go beyond simple two-state unfolding. Exploiting this finding, we report the first high-resolution structural models of the urea denaturation process of an alpha-helical membrane-associated protein and its completely unfolded state, which contains almost no regular secondary structure but nevertheless retains a topology close to that of the folded state.