Urea and Guanidinium Induced Denaturation of a Trp-Cage Miniprotein

• Published in: The journal of physical chemistry. B Vol. 115; no. 28; pp. 8910 - 8924
• Main Authors: Heyda, Jan, Kožíšek, Milan, Bednárova, Lucie, Thompson, Gary, Konvalinka, Jan, Vondrášek, Jiří, Jungwirth, Pavel
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 21.07.2011
• Subjects: B: Biophysical Chemistry; Calorimetry, Differential Scanning; Circular Dichroism; Denaturation; Dichroism; Differential scanning calorimetry; Femtosecond; Guanidine - chemistry; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular dynamics; Physical chemistry; Protein Denaturation; Simulation; Tryptophan - chemistry; Urea - chemistry; Ureas
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp200790h

Using a combination of experimental techniques (circular dichroism, differential scanning calorimetry, and NMR) and molecular dynamics simulations, we performed an extensive study of denaturation of the Trp-cage miniprotein by urea and guanidinium. The experiments, despite their different sensitivities to various aspects of the denaturation process, consistently point to simple, two-state unfolding process. Microsecond molecular dynamics simulations with a femtosecond time resolution allow us to unravel the detailed molecular mechanism of Trp-cage unfolding. The process starts with a destabilizing proline shift in the hydrophobic core of the miniprotein, followed by a gradual destruction of the hydrophobic loop and the α-helix. Despite differences in interactions of urea vs guanidinium with various peptide moieties, the overall destabilizing action of these two denaturants on Trp-cage is very similar.