Stability and Folding Kinetics of a Ubiquitin Mutant with a Strong Propensity for Nonnative β-Hairpin Conformation in the Unfolded State

• DOI: 10.1021/bi030147d
• Publication Date: 2003-11-18T10:36:33Z
• Authors: Geoffrey W. Platt; Stephen A. Simpson; Robert Layfield; Mark S. Searle
• Keywords: Folding (DSP implementation); Protein tertiary structure

A F45W mutant of yeast ubiquitin has been used as a model system to examine the effects nonnative local interactions on protein folding and stability. Mutating native TLTGK G-bulged type I turn in N-terminal β-hairpin NPDG stabilizes β-strand alignment isolated peptide fragment. However, NMR structural analysis proteins shows that is forced adopt an unfavorable turn. The significantly less stable (∼9 kJ mol-1) folds 30 times slower than sequence, demonstrating can modulate stability attainment nativelike conformation transition state ensemble frustrated by mutations. Surprising, alcoholic cosolvents [5−10% (v/v) TFE] are shown accelerate rate mutant. We conclude, backed-up data fragments, even though states denatured highly populated their further enhanced presence cosolvents, simultaneous increase proportion secondary structure (hairpin or helix), rapid equilibrium with states, sufficient process. It evident modulating increasing propensities change kinetics. nonlocal contacts formed global cooperative event appear determine specificity.