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Protein cold denaturation as seen from the solvent

Davidovic, Monika LU ; Mattea, Carlos LU ; Qvist, Johan LU and Halle, Bertil LU (2009) In Journal of the American Chemical Society 131(3). p.1025-1036
Abstract
Unlike most ordered molecular systems, globular proteins exhibit a temperature of maximum stability, implying that the structure can be disrupted by cooling. This cold denaturation phenomenon is usually linked to the temperature-dependent hydrophobic driving force for protein folding. Yet, despite the key role played by protein−water interactions, hydration changes during cold denaturation have not been investigated experimentally. Here, we use water−17O spin relaxation to monitor the hydration dynamics of the proteins BPTI, ubiquitin, apomyoglobin, and β-lactoglobulin in aqueous solution from room temperature down to −35 °C. To access this temperature range without ice formation, we contained the protein solution in nonperturbing... (More)
Unlike most ordered molecular systems, globular proteins exhibit a temperature of maximum stability, implying that the structure can be disrupted by cooling. This cold denaturation phenomenon is usually linked to the temperature-dependent hydrophobic driving force for protein folding. Yet, despite the key role played by protein−water interactions, hydration changes during cold denaturation have not been investigated experimentally. Here, we use water−17O spin relaxation to monitor the hydration dynamics of the proteins BPTI, ubiquitin, apomyoglobin, and β-lactoglobulin in aqueous solution from room temperature down to −35 °C. To access this temperature range without ice formation, we contained the protein solution in nonperturbing picoliter emulsion droplets. Among the four proteins, only the destabilized apomyoglobin was observed to cold denature. Ubiquitin was found to be thermodynamically stable at least down to −32 °C, whereas β-lactoglobulin is expected to be unstable below −5 °C but remains kinetically trapped in the native state. When destabilized by 4 M urea, β-lactoglobulin cold denatures at 10 °C, as found previously by other methods. As seen from the solvent, the cold-denatured states of apomyoglobin in water and β-lactoglobulin in 4 M urea are relatively compact and are better described as solvent-penetrated than as unfolded. This finding challenges the popular analogy between cold denaturation and the anomalous low-temperature increase in aqueous solubility of nonpolar molecules. Our results also suggest that the reported cold denaturation at −20 °C of ubiquitin encapsulated in reverse micelles is caused by the low water content rather than by the low temperature. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
131
issue
3
pages
1025 - 1036
publisher
The American Chemical Society
external identifiers
  • wos:000264791600042
  • scopus:61749085446
ISSN
1520-5126
DOI
10.1021/ja8056419
language
English
LU publication?
yes
id
59bb1196-24eb-433d-9855-9f47e2375da3 (old id 1292741)
date added to LUP
2009-02-17 17:15:36
date last changed
2017-10-22 03:58:13
@article{59bb1196-24eb-433d-9855-9f47e2375da3,
  abstract     = {Unlike most ordered molecular systems, globular proteins exhibit a temperature of maximum stability, implying that the structure can be disrupted by cooling. This cold denaturation phenomenon is usually linked to the temperature-dependent hydrophobic driving force for protein folding. Yet, despite the key role played by protein−water interactions, hydration changes during cold denaturation have not been investigated experimentally. Here, we use water−17O spin relaxation to monitor the hydration dynamics of the proteins BPTI, ubiquitin, apomyoglobin, and β-lactoglobulin in aqueous solution from room temperature down to −35 °C. To access this temperature range without ice formation, we contained the protein solution in nonperturbing picoliter emulsion droplets. Among the four proteins, only the destabilized apomyoglobin was observed to cold denature. Ubiquitin was found to be thermodynamically stable at least down to −32 °C, whereas β-lactoglobulin is expected to be unstable below −5 °C but remains kinetically trapped in the native state. When destabilized by 4 M urea, β-lactoglobulin cold denatures at 10 °C, as found previously by other methods. As seen from the solvent, the cold-denatured states of apomyoglobin in water and β-lactoglobulin in 4 M urea are relatively compact and are better described as solvent-penetrated than as unfolded. This finding challenges the popular analogy between cold denaturation and the anomalous low-temperature increase in aqueous solubility of nonpolar molecules. Our results also suggest that the reported cold denaturation at −20 °C of ubiquitin encapsulated in reverse micelles is caused by the low water content rather than by the low temperature.},
  author       = {Davidovic, Monika and Mattea, Carlos and Qvist, Johan and Halle, Bertil},
  issn         = {1520-5126},
  language     = {eng},
  number       = {3},
  pages        = {1025--1036},
  publisher    = {The American Chemical Society},
  series       = {Journal of the American Chemical Society},
  title        = {Protein cold denaturation as seen from the solvent},
  url          = {http://dx.doi.org/10.1021/ja8056419},
  volume       = {131},
  year         = {2009},
}