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    Mapping the topography of a protein energy landscape

    Hutton, R.D. and Wilkinson, J. and Faccin, M. and Sivertsson, E.M. and Pelizzola, A. and Lowe, Alan R. and Bruscolini, P. and Itzhaki, L.S. (2015) Mapping the topography of a protein energy landscape. Journal of the American Chemical Society 137 (46), pp. 14610-14625. ISSN 0002-7863.

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    Abstract

    Protein energy landscapes are highly complex, yet the vast majority of states within them tend to be invisible to experimentalists. Here, using site-directed mutagenesis and exploiting the simplicity of tandem-repeat protein structures, we delineate a network of these states and the routes between them. We show that our target, gankyrin, a 226-residue 7-ankyrin-repeat protein, can access two alternative (un)folding pathways. We resolve intermediates as well as transition states, constituting a comprehensive series of snapshots that map early and late stages of the two pathways and show both to be polarized such that the repeat array progressively unravels from one end of the molecule or the other. Strikingly, we find that the protein folds via one pathway but unfolds via a different one. The origins of this behavior can be rationalized using the numerical results of a simple statistical mechanics model that allows us to visualize the equilibrium behavior as well as single-molecule folding/unfolding trajectories, thereby filling in the gaps that are not accessible to direct experimental observation. Our study highlights the complexity of repeat-protein folding arising from their symmetrical structures; at the same time, however, this structural simplicity enables us to dissect the complexity and thereby map the precise topography of the energy landscape in full breadth and remarkable detail. That we can recapitulate the key features of the folding mechanism by computational analysis of the native structure alone will help toward the ultimate goal of designed amino-acid sequences with made-to-measure folding mechanisms—the Holy Grail of protein folding.

    Metadata

    Item Type: Article
    School: Birkbeck Schools and Departments > School of Science > Biological Sciences
    Research Centre: Structural Molecular Biology, Institute of (ISMB)
    Depositing User: Administrator
    Date Deposited: 30 Nov 2015 13:55
    Last Modified: 26 Jul 2019 23:30
    URI: http://eprints.bbk.ac.uk/id/eprint/13647

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