Department of Biology, Johns Hopkins University, Baltimore, MD 21218-2685, United States.
Biophys Chem. 2010 Oct;151(3):149-54. doi: 10.1016/j.bpc.2010.06.004. Epub 2010 Jun 23.
The varied selectivity of bZIP transcription factors stems from the fact that they are dimers consisting of two not necessarily identical subunits held together by a leucine zipper dimerization domain. Determining their stability is therefore important for understanding the mechanism of formation of these transcription factors. The most widely used approach for this problem consists of observing temperature-induced dissociation of the bZIPs by any means sensitive to their structural changes, particularly optical methods. In calculating thermodynamic characteristics of this process from such data it is usually assumed that it represents a two-state transition. However, scanning micro-calorimetric study of the temperature-induced unfolding/dissociation of the three bZIPs formed by the ATF-2 and c-Jun proteins, i.e. the two homodimers (ATF-2/ATF-2) and (c-Jun/c-Jun) and the heterodimer (ATF-2/c-Jun), showed that this process does not represent a two-state transition, as found previously with the GCN4 homodimeric bZIP protein. This raises doubt about all indirect estimates of bZIP thermodynamic characteristics based on analysis of their optically-observed temperature-induced changes.
bZIP 转录因子的选择性多种多样，这是因为它们是由两个不一定相同的亚基组成的二聚体，通过亮氨酸拉链二聚化结构域结合在一起。因此，确定它们的稳定性对于理解这些转录因子的形成机制非常重要。解决这个问题最常用的方法是通过任何对结构变化敏感的方法，特别是光学方法，观察 bZIP 因温度诱导而发生的解离。在从这些数据中计算这个过程的热力学特性时，通常假设它代表一个两态转变。然而，对由 ATF-2 和 c-Jun 蛋白形成的三种 bZIP（即两个同源二聚体（ATF-2/ATF-2）和（c-Jun/c-Jun）以及异源二聚体（ATF-2/c-Jun））的温度诱导解折叠/解离的扫描微量量热研究表明，与先前用 GCN4 同源二聚体 bZIP 蛋白观察到的情况一样，这个过程不代表两态转变。这使得所有基于对其光学观察到的温度诱导变化进行分析的 bZIP 热力学特性的间接估计都受到了质疑。
