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Kinetic Role of Electrostatic Interactions in the Unfolding of Hyperthermophilic and Mesophilic Rubredoxins

Cavagnero, Silvia and Debe, Derek A. and Zhou, Zhi H. and Adams, Michael W. W. and Chan, Sunney I. (1998) Kinetic Role of Electrostatic Interactions in the Unfolding of Hyperthermophilic and Mesophilic Rubredoxins. Biochemistry, 37 (10). pp. 3369-3376. ISSN 0006-2960. http://resolver.caltech.edu/CaltechAUTHORS:20180524-152540450

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Abstract

The temperature dependence of the unfolding kinetics of rubredoxins from the hyperthermophile Pyrococcus furiosus (RdPf) and the mesophile Clostridium pasteurianum (RdCp) has been studied. Results show that RdPf unfolds much more slowly, under all experimentally accessible temperature regimes, than RdCp and other typical mesophilic proteins. Rates of RdCp and RdPf unfolding decrease upon increasing the pH above 2 and diverge dramatically at pH 7. As shown by detailed electrostatic energy calculations, this is the result of a differential degree of protonation of the negatively charged amino acids, which causes distinct electrostatic configurations as a function of pH. We propose that ion pairs, particularly those that are placed in key surface positions, may play a kinetic role by mildly clamping the protein and thereby influencing the nature and the number of the vibrational normal modes that are thermally accessible upon unfolding. More generally, these modes are also likely to be affected by the favorable electrostatic configurations, which we have shown to be directly linked to the extremely slow unfolding rates of RdPf at neutral pH. Even at pH 2, in the absence of any salt bridges, the unfolding rates of RdPf are much smaller than those of RdCp. This is ascribed to presently unidentified structural elements of nonelectrostatic nature. Since electrostatic effects influence the unfolding kinetics of both mesophilic and thermophilic rubredoxins, these findings may be of general significance for proteins.


Item Type:Article
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https://dx.doi.org/10.1021/bi9721795DOIArticle
ORCID:
AuthorORCID
Chan, Sunney I.0000-0002-5348-2723
Additional Information:© 1998 American Chemical Society. Received September 3, 1997. We thank Prof. Doug Rees and Dr. Reginald Waldeck for helpful discussions and critical comments on this work.
Record Number:CaltechAUTHORS:20180524-152540450
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180524-152540450
Official Citation:Kinetic Role of Electrostatic Interactions in the Unfolding of Hyperthermophilic and Mesophilic Rubredoxins Silvia Cavagnero, Derek A. Debe, Zhi H. Zhou, Michael W. W. Adams, and Sunney I. Chan Biochemistry 1998 37 (10), 3369-3376 DOI: 10.1021/bi9721795
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86599
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:24 May 2018 22:35
Last Modified:24 May 2018 22:35

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