Seelig S, Oppenheimer J H
J Biol Chem. 1982 Feb 10;257(3):1378-82.
We have investigated the thermodynamic properties of triiodothyronine (T3)-solubilized hepatic nuclear receptor interaction. These studies revealed that the equilibrium constant was markedly dependent on temperature and van't Hoff plots revealed a significant deviation from linearity. Both enthalpy and entropy changes decreased with increasing temperature such that at 37 degrees C both were negative. (delta H0 -27.1 kcal/mol; delta S0, -45.1 cal/mol.deg; and the heat capacity delta Cp0 (25 degrees C), -759 cal/mol.deg). Several T3 analogues revealed similar thermodynamic characteristics. Our finding that the T3-receptor interaction is characterized by a negative heat capacity is compatible with the previous proposal of hydrophobic bonding by Jorgensen. The large negative entropy change at 37 degrees C for T3-receptor reaction is in contrast to the more positive entropy values for several T3-plasma protein reactions. One possible explanation of this difference in entropy values between the nuclear receptor and plasma proteins is that T3 induces a conformational change in the receptor, a concept supported by previous data from our laboratory indicating that the occupation of the T3 receptor results in an alteration in the chromatographic migration of the receptor.
我们研究了三碘甲状腺原氨酸（T3）溶解的肝细胞核受体相互作用的热力学性质。这些研究表明，平衡常数明显依赖于温度，范特霍夫图显示出与线性关系有显著偏差。焓变和熵变均随温度升高而降低，以至于在37℃时两者均为负值。（ΔH0 -27.1千卡/摩尔；ΔS0，-45.1卡/摩尔·度；以及热容ΔCp0（25℃），-759卡/摩尔·度）。几种T3类似物显示出相似的热力学特征。我们发现T3-受体相互作用的特征是负的热容，这与约根森先前提出的疏水键合观点相符。T3-受体反应在37℃时出现的大的负熵变与几种T3-血浆蛋白反应中更正值的熵值形成对比。核受体和血浆蛋白之间熵值差异的一种可能解释是，T3诱导受体发生构象变化，我们实验室先前的数据支持这一概念，这些数据表明T3受体的占据会导致受体色谱迁移的改变。
