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Folding of circular permutants with decreased contact order: general trend balanced by protein stability
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
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2001 (English)In: Journal of Molecular Biology, ISSN 0022-2836, Vol. 314, no 4, 891-900 p.Article in journal (Refereed) Published
Abstract [en]

To examine the influence of contact order and stability on the refolding rate constant for two-state proteins, we have analysed the folding kinetics of the small β-α-β protein S6 and two of its circular permutants with relative contact orders of 0.19, 0.15 and 0.12. Data reveal a small but significant increase of the refolding rate constant (log kf) with decreasing contact order. At the same time, the decreased contact order is correlated to losses in global stability and alterations of the folding nucleus. When the differences in stability are accounted for by addition of Na2SO4 or by comparison of the folding kinetics at the transition mid-point, the dependence between log kf and contact order becomes stronger and follows the general correlation for two-state proteins. The observation emphasizes the combined action of topology and stability in controlling the rate constant of protein folding.

Place, publisher, year, edition, pages
2001. Vol. 314, no 4, 891-900 p.
Keyword [en]
protein folding, rate constants, two-state proteins, topology, protein stability
URN: urn:nbn:se:umu:diva-8780DOI: doi:10.1006/jmbi.2001.5186OAI: diva2:148451
Jeanette Hargbo.Available from: 2008-02-12 Created: 2008-02-12 Last updated: 2009-08-13Bibliographically approved
In thesis
1. Protein Folding Studies on the Ribosomal Protein S6: the Role of Entropy in Nucleation
Open this publication in new window or tab >>Protein Folding Studies on the Ribosomal Protein S6: the Role of Entropy in Nucleation
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the most challenging tasks remaining in the field of biochemistry is the one of understanding how the information within the amino acid sequence of proteins translates into a unique structure. Solving this problem would lead to endless possibilities for application in the medical and biotechnology industry.

Many decades ago scientists realized that the process that facilitates the folding of a polypeptide chain could not be random and happen by chance; there needs to be direction in the folding free energy landscape. This landscape is defined by the thermodynamic factors entropy and enthalpy. The contribution made by enthalpy i.e. the contact energies from intra- and intermolecular interactions have been extensively investigated by various mutational studies. The influence of entropy on the other hand, is less well understood. My work focuses on the effect of altering the entropic components of forming the various parts of a known protein scaffold. This is done by genetic engineering in combination with biophysical characterisation and analysis. The results show effects on protein folding rates as well as on the pathway for nucleation and emphasis the ability of the folding landscape to readjust to entropic variations. Proteins are therefore not required to fold along a unique route to their final structure but can do so in several ways. The folding pathways we observe today have hence likely evolved as an adaptation to biological demands.

Place, publisher, year, edition, pages
Umeå: Kemi, 2005. 150 p.
Biochemistry, protein folding, circular permutation, topology, connectivity, entropy, protein stability, chevron plot, Biokemi
National Category
Biochemistry and Molecular Biology
Research subject
urn:nbn:se:umu:diva-535 (URN)91-7305-890-4 (ISBN)
Public defence
2005-06-03, KB3A9, KBC, Umeå universitet, Umeå, 13:00 (English)
Available from: 2005-05-10 Created: 2005-05-10 Last updated: 2009-08-13Bibliographically approved

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