COUPLED ASSOCIATION & SEQUENCE SPECIFIC PROTEIN DNA FOLDING: CALORIMETRY

特定蛋白质-DNA复合体的形成表现为 显著的负热容量变化。这已经被考虑过了 作为疏水作用力在复合体中起主导作用的证据 队形。然而，在许多情况下，这种交互会导致 蛋白质和DNA的结构变化。目前仍不清楚， 值得商榷的是，观察到的热容变化应该达到什么程度 简单地归因于自由成分的关联或 伴随着绑定而来的结构性变化。两个实验系统 考虑的是：小鼠HMG盒的序列特异性复合体 带有不同长度和62个氨基酸长度的DNA靶标的SOX-5 酵母转录因子Gcn4片段与密码子 AP1和ATF/CREB相关位点。在这两种情况下，DNA结合域 在很大程度上是分离无序的，因此， 与DNA的结合必然涉及到同时的折叠。论 另一方面，DNA双链也经历了解开和弯曲 复杂的队形。能量参数的测定 描述缔合与非缔合之间的热力学耦合 组件的结构重新安排将 通过ITC和DSC的结合来实现。

Formation of specific protein-DNA complexes is manifested by a significant negative heat capacity change. This has been considered as evidence for hydrophobic forces playing dominant role in complex formation. However, in many cases the interaction results in structural changes in both, protein and DNA. It remains unclear and debatable to what extent the observed changes in heat capacity should be attributed simply to association of free components or to structural changes that accompany binding. Two experimental systems are considered: the sequence-specific complexes of the mouse HMG box Sox-5 with DNA targets of different length and of the 62 AA long fragment of the yeast transcriptional factor GCN4 with the closely related AP1 and ATF/CREB sites. In both cases the DNA-binding domain of the protein is largely disordered in isolation and, therefore, binding to DNA necessarily involves simultaneous refolding. On the other hand, the DNA duplex also undergoes unwinding and bending upon complex formation. The determination of the energetic parameters that characterize the thermodynamic coupling between association and structural rearrangements of components will be accomplished by combination of ITC and DSC.