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Biophys. J. BioFAST: First Published November 5, 2004. doi:10.1529/biophysj.104.050435
© 2004 by the Biophysical Society.

A more recent version of this article appeared on February 1, 2005.
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PROTEINS

Pressure Equilibrium and Jump Study on Unfolding of 23kDa Protein from Spinach Photosystem II

Cui-Yan Tan 1, Chun-He Xu 2, Jun Weng 3, Jian-Ren Shen 4, Shinsuke Sakuma 5, Yasushi Yamamoto 5, Renhard Lane 6, Claude Balny 6 and Kangcheng Ruan 1*

1 Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, the Chinese
2 Institute of Plant Physiology, Shanghai Institutes for Biological Sciences, the Chinese Academy of
3 Institute of Plant Physiology, Shanghai Institutes for Biological Sciences, the Chinese Academy of S
4 Department of Biology, Faculty of Science, Okayama
5 Graduate School of Natural Science
6 Institute National de la Santè et de la Recherche Mèdicale, INSERM U 128

* To whom correspondence should be addressed. E-mail: kcruan{at}sibs.ac.cn.

Submitted on August 9, 2004
Revised on September 7, 2004
Accepted on 21 October 2004


  Abstract
Pressure-induced unfolding of 23kDa protein from spinach photosystem II(termed as P23k) has been systematically investigated at various experimental conditions. Thermodynamic equilibrium studies indicate that the protein is very sensitive to pressure. At 20 °C and pH 5.5, P23k shows a reversible two-state unfolding transition under pressure with a midpoint near 160 Mpa, a pressure much lower than those observed for unfolding of most natural proteins studied to date. The free energy and volume change for the unfolding are 5.9 kcal/mol and - 160 ml/mol respectively. It was found NaCl and glycerol significantly stabilize the protein from unfolding and the stabilization is associated not only with the increase in the free energy but also with the decrease in the volume change upon unfolding. The pressure-jump studies of P23k reveal a negative activation volume for unfolding (- 66.2 ml/mol) and a positive activation volume for refolding (84.1 ml/mol), indicating that in terms of system volume, the protein transition state lies between the folded and unfolded states. Studying on the temperature dependence of the activation volume indicates that the thermal expansitivity of the transition state and the unfolded state of P23k are closer each other and larger than the native state. The divers pressure-refolding pathways of P23k in some conditions were revealed in pressure-jump kinetics.

Key Words: 23kDa protein, fluorescence, hydrostatic pressure, photosystem II, pressure jump, protein folding/unfolding




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J. Font, J. Torrent, M. Ribo, D. V. Laurents, C. Balny, M. Vilanova, and R. Lange
Pressure-Jump-Induced Kinetics Reveals a Hydration Dependent Folding/Unfolding Mechanism of Ribonuclease A
Biophys. J., September 15, 2006; 91(6): 2264 - 2274.
[Abstract] [Full Text] [PDF]


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Copyright © 2004 by the Biophysical Society.