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The Changing Nature of the Protein Folding Transition State: Implications for the Shape of the Free-energy Profile for Folding

Oliveberg, Mikael LU ; Tan, Yee-Joo; Silow, Maria and Fersht, Alan R (1998) In Journal of Molecular Biology 277(4). p.933-943
Abstract
According to landscape theory proteins do not fold by localised pathways, but find their native conformation by a progressive organisation of an ensemble of partly folded structures down a folding funnel. Here, we use kinetics and protein engineering to investigate the shape of the free-energy profile for two-state folding, which is the macroscopic view of the funnel process for small and rapidly folding proteins. Our experiments are based mainly on structural changes of the transition state of chymotrypsin inhibitor 2 (CI2) upon destabilisation with temperature and GdnHCl. The transition state ensemble of CI2 is a localised feature in the free-energy profile that is sharply higher than the other parts of the activation barrier. The... (More)
According to landscape theory proteins do not fold by localised pathways, but find their native conformation by a progressive organisation of an ensemble of partly folded structures down a folding funnel. Here, we use kinetics and protein engineering to investigate the shape of the free-energy profile for two-state folding, which is the macroscopic view of the funnel process for small and rapidly folding proteins. Our experiments are based mainly on structural changes of the transition state of chymotrypsin inhibitor 2 (CI2) upon destabilisation with temperature and GdnHCl. The transition state ensemble of CI2 is a localised feature in the free-energy profile that is sharply higher than the other parts of the activation barrier. The relatively fixed position of the CI2 transition state on the reaction coordinate makes it easy to characterise but contributes also to overshadow the rest of the free-energy profile, the shape of which is inaccessible for analysis. Results from mutants of CI2 and comparison with other two-state proteins, however, point at the possibility that the barrier for folding is generally broad and that localised transition states result from minor ripples in the free-energy profile. Accordingly, variabilities in the folding kinetics may not indicate different folding mechanisms, but could be accounted for by various degrees of ruggedness on top of very broad activation barriers for folding. The concept is attractive since it summarises a wide range of folding data which have previously seemed unrelated. It is also supported by theory. Consistent with experiment, broad barriers predict that new transition state ensembles are exposed upon extreme destabilisation or radical mutations. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
protein folding, transition state, CI2, protein engineering, energy landscape
in
Journal of Molecular Biology
volume
277
issue
4
pages
933 - 943
publisher
Elsevier
external identifiers
  • scopus:0032503027
ISSN
1089-8638
DOI
10.1006/jmbi.1997.1612
language
English
LU publication?
yes
id
7fcdade7-e998-4a76-a89d-5be8f05e37da (old id 125586)
date added to LUP
2007-07-09 09:46:23
date last changed
2017-05-07 04:12:43
@article{7fcdade7-e998-4a76-a89d-5be8f05e37da,
  abstract     = {According to landscape theory proteins do not fold by localised pathways, but find their native conformation by a progressive organisation of an ensemble of partly folded structures down a folding funnel. Here, we use kinetics and protein engineering to investigate the shape of the free-energy profile for two-state folding, which is the macroscopic view of the funnel process for small and rapidly folding proteins. Our experiments are based mainly on structural changes of the transition state of chymotrypsin inhibitor 2 (CI2) upon destabilisation with temperature and GdnHCl. The transition state ensemble of CI2 is a localised feature in the free-energy profile that is sharply higher than the other parts of the activation barrier. The relatively fixed position of the CI2 transition state on the reaction coordinate makes it easy to characterise but contributes also to overshadow the rest of the free-energy profile, the shape of which is inaccessible for analysis. Results from mutants of CI2 and comparison with other two-state proteins, however, point at the possibility that the barrier for folding is generally broad and that localised transition states result from minor ripples in the free-energy profile. Accordingly, variabilities in the folding kinetics may not indicate different folding mechanisms, but could be accounted for by various degrees of ruggedness on top of very broad activation barriers for folding. The concept is attractive since it summarises a wide range of folding data which have previously seemed unrelated. It is also supported by theory. Consistent with experiment, broad barriers predict that new transition state ensembles are exposed upon extreme destabilisation or radical mutations.},
  author       = {Oliveberg, Mikael and Tan, Yee-Joo and Silow, Maria and Fersht, Alan R},
  issn         = {1089-8638},
  keyword      = {protein folding,transition state,CI2,protein engineering,energy landscape},
  language     = {eng},
  number       = {4},
  pages        = {933--943},
  publisher    = {Elsevier},
  series       = {Journal of Molecular Biology},
  title        = {The Changing Nature of the Protein Folding Transition State: Implications for the Shape of the Free-energy Profile for Folding},
  url          = {http://dx.doi.org/10.1006/jmbi.1997.1612},
  volume       = {277},
  year         = {1998},
}