Molecular Determinants of Expansivity of Native Globular Proteins: A Pressure Perturbation Calorimetry Study

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• 作者：Daniel Vasilchuk ; Pranav P. Pandharipande ; Saba Suladze ; Jose M. Sanchez-Ruiz ; George I. Makhatadze
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：June 12, 2014
• 年：2014
• 卷：118
• 期：23
• 页码：6117-6122
• 全文大小：371K
• 年卷期：v.118,no.23(June 12, 2014)
• ISSN：1520-5207

文摘

There is a growing interest in understanding how hydrostatic pressure (P) impacts the thermodynamic stability (螖G) of globular proteins. The pressure dependence of stability is defined by the change in volume upon denaturation, 螖V = (鈭偽?i>G/鈭?i>P)_T. The temperature dependence of change in volume upon denaturation itself is defined by the changes in thermal expansivity (螖E), 螖E = (鈭偽?i>V/鈭?i>T)_P. The pressure perturbation calorimetry (PPC) allows direct experimental measurement of the thermal expansion coefficient, 伪 = E/V, of a protein in the native, 伪_N(T), and unfolded, 伪_U(T), states as a function of temperature. We have shown previously that 伪_U(T) is a nonlinear function of temperature but can be predicted well from the amino acid sequence using 伪(T) values for individual amino acids (J. Phys. Chem. B 2010, 114, 16166鈥?6170). In this work, we report PPC results on a diverse set of nine proteins and discuss molecular factors that can potentially influence the thermal expansion coefficient, 伪_N(T), and the thermal expansivity, E_N(T), of proteins in the native state. Direct experimental measurements by PPC show that 伪_N(T) and E_N(T) functions vary significantly for different proteins. Using comparative analysis and site-directed mutagenesis, we have eliminated the role of various structural or thermodynamic properties of these proteins such as the number of amino acid residues, secondary structure content, packing density, electrostriction, dynamics, or thermostability. We have also shown that 伪_N(T) and E_N,sp(T) functions for a given protein are rather insensitive to the small changes in the amino acid sequence, suggesting that 伪_N(T) and E_N(T) functions might be defined by a topology of a given protein fold. This conclusion is supported by the similarity of 伪_N(T) and E_N(T) functions for six resurrected ancestral thioredoxins that vary in sequence but have very similar tertiary structure.