Nature Structural Biology
3, 613 - 618 (1996)
doi:10.1038/nsb0796-613
Refolding and unfolding kinetics of the equilibrium folding intermediate of apomyoglobinMarc Jamin1
& Robert L. Baldwin1
1Department of Biochemistry, Stanford University Medical Center, Stanford, California 94305-5307, USA Little is known about the kinetic process in which stable intermediates in protein folding are formed: whether their folding is highly cooperative (two-state) or weakly cooperative is controversial. We report here that the folding and unfolding kinetics of the pH 4-stable intermediate (I1) of apomyoglobin are measurable, in the millisecond time range, when monitored by stopped-flow measurements of tryptophan fluorescence. The kinetics confirm that folding of I1 is strongly cooperative, but there is a burst phase (missing amplitude) in unfolding. If the faster steps in unfolding of I1 can be measured directly by suitable fast-reaction methods, they will give information about the nature of the folding transition.
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