Protein folding and unfolding in microseconds to nanoseconds by experiment and simulation.

Mayor, U; Johnson, C M; Daggett, V; Fersht, A R · Proc Natl Acad Sci U S A · 2000

basic_science · Level V

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Abstract

The Engrailed Homeodomain protein has the highest refolding and unfolding rate constants directly observed to date. Temperature jump relaxation measurements gave a refolding rate constant of 37,500 s(-1) in water at 25 degrees C, rising to 51,000 s(-1) around 42 degrees C. The unfolding rate constant was 1,100 s(-1) in water at 25 degrees C and 205,000 s(-1) at 63 degrees C. The unfolding half-life is extrapolated to be approximately 7.5 ns at 100 degrees C, which allows real-time molecular dynamics unfolding simulations to be tested on this system at a realistic temperature. Preliminary simulations did indeed conform to unfolding on this time scale. Further, similar transition states were observed in simulations at 100 degrees C and 225 degrees C, suggesting that high-temperature simulations provide results applicable to lower temperatures.

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