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J Am Chem Soc. 2008 Jun 18;130(24):7540-1. doi: 10.1021/ja801941r. Epub 2008 May 22.

Probing the bottom of a folding funnel using conformationally gated electron transfer reactions.

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  • 1Department of Chemistry and Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, Montana 59812, USA.

Abstract

The effect of global stability on the kinetics of interconversion between the native (N) and a compact, partially unfolded form (I) of iso-1-cytochrome c stabilized by His73-heme ligation is investigated using a novel conformationally gated ET method. For the K73H variant and the 2-fold less stable AcH73 variant, the N and I conformers are of nearly equal stability at pH 7.5. The pH jump kinetic data yield kobs = kNI + kIN of 35-40 s-1 at final pH values from 6 to 8 for the AcH73 variant, about 3-fold faster than for the more stable K73H variant. Gated ET measurements give kNI = 28 s-1 and kIN = 13 s-1 for the AcH73 variant, 10- and 2-fold greater than that for the more stable K73H variant. Thus, funneled landscapes have evolved such that loss of global stability lowers barriers at the bottom of a folding funnel, still allowing for efficient folding.

PMID:
18494471
[PubMed - indexed for MEDLINE]
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