Probing the folding transition state of ubiquitin mutants by temperature-jump-induced downhill unfolding.

ABSTRACT: Crucial to revealing mechanistic details of protein folding is a characterization of the transition state ensemble and its structural dynamics. To probe the transition state of ubiquitin thermal unfolding, we examine unfolding dynamics and kinetics of wild-type and mutant ubiquitin using time-resolved nonlinear infrared spectroscopy after a nanosecond temperature jump. We observe spectral changes on two different time scales. A fast nonexponential microsecond phase is attributed to downhill unfolding from the transition state region, which is induced by a shift of the barrier due to the rapid temperature change. Slow millisecond changes arise from thermally activated folding and unfolding kinetics. Mutants that stabilize or destabilize beta strands III-V lead to a decreased or increased am

SUBMITTER: Chung HS 

PROVIDER: S-EPMC3319365 | biostudies-literature | 2008 Dec

REPOSITORIES: biostudies-literature