Pressure equilibrium and jump study on unfolding of 23-kDa protein from spinach photosystem II.
Pressure equilibrium and jump study on unfolding of 23-kDa protein from spinach photosystem II.
复制标题
DOI：
10.1529/biophysj.104.050435
复制
发表时间：
2005-02
影响因子：
3.4
通讯作者：
Cui-yan Tan;Chun-he Xu;J. Wong;Jian-Ren Shen;Shinsuke Sakuma;Yasusi Yamamoto;R. Lange;C. Balny;K. Ruan
中科院分区：
文献类型：
--
作者：
Cui-yan Tan;Chun-he Xu;J. Wong;Jian-Ren Shen;Shinsuke Sakuma;Yasusi Yamamoto;R. Lange;C. Balny;K. Ruan
压力诱导展开的23-kDa的蛋白质从菠菜光系统II已系统地研究在各种实验条件下。热力学平衡研究表明，蛋白质是非常敏感的压力。在20 ℃和pH 5.5下，23-kDa蛋白质在压力下显示出可逆的两态解折叠转变，中点接近160 MPa，这比迄今为止研究的大多数天然蛋白质低得多。解折叠的自由能（Δ G（u））和体积变化（Δ V（u））分别为5.9 kcal/mol和-160 ml/mol。发现NaCl和蔗糖显著稳定蛋白质使其不展开，并且该稳定不仅与DeltaG（u）的增加相关，而且与DeltaV（u）的降低相关。23-kDa蛋白质的压力跃变研究揭示了展开的负活化体积（-66.2 ml/mol）和重折叠的正活化体积（84.1 ml/mol），表明就系统体积而言，蛋白质过渡态位于折叠和展开状态之间。温度对展开动力学的影响的检查表明，23-kDa蛋白质的过渡态和展开态的热膨胀性彼此更接近，并且它们大于天然状态的热膨胀性。压力跃变动力学揭示了23-kDa蛋白在某些条件下的不同压力复性途径。
Pressure-induced unfolding of 23-kDa protein from spinach photosystem II has been systematically investigated at various experimental conditions. Thermodynamic equilibrium studies indicate that the protein is very sensitive to pressure. At 20 degrees C and pH 5.5, 23-kDa protein shows a reversible two-state unfolding transition under pressure with a midpoint near 160 MPa, which is much lower than most natural proteins studied to date. The free energy (DeltaG(u)) and volume change (DeltaV(u)) for the unfolding are 5.9 kcal/mol and -160 ml/mol, respectively. It was found that NaCl and sucrose significantly stabilize the protein from unfolding and the stabilization is associated not only with an increase in DeltaG(u) but also with a decrease in DeltaV(u). The pressure-jump studies of 23-kDa protein 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. Examination of the temperature effect on the unfolding kinetics indicates that the thermal expansibility of the transition state and the unfolded state of 23-kDa protein are closer to each other and they are larger than that of the native state. The diverse pressure-refolding pathways of 23-kDa protein in some conditions were revealed in pressure-jump kinetics.