CALORIMETRIC TITRATION OF GALACTOSE BINDING TO GAL REPRESSOR OF E COLI

大肠杆菌的半乳糖操纵子是一个经典的负阻遏子系统。 它包含三个基因，这些基因编码的是 半乳糖代谢。GalR，GAL抑制因子，调节 从这部歌剧改编而来。其功能涉及多个环节 平衡包括基本的阻遏子-诱导子结合和 抑制子-操作者的相互作用。GalR单体-二聚体平衡和 可能与其他调节蛋白(HU和cAMP-CRP)相互作用 在体内功能中发挥重要作用。大小和联系 这些相互作用中的一部分可以通过物理研究在体外进行探索。 内源性色氨酸荧光用于表征 GalR：D-半乳糖结合与温度的关系。装订 看起来很合作，至少在低温下是这样，估计 范氏热焓为-2.5千卡/摩尔。直接量热法 配体结合的热力学参数的测定 GalR将提高我们对能量学和变构的理解 此对象中的 系统，以及一般的转录调控。

The gal operon of E. coli is a classic negative repression system that contains three genes which encode for enzymes required in galactose metabolism. GalR, the gal repressor, regulates transcription from this operon. Its function involves multiple linked equilibria including the basic repressor-inducer binding and repressor-operator interactions. A GalR monomer-dimer equilibrium and interactions with other regulatory proteins (Hu and cAMP-CRP) probably play important roles in in vivo function. The magnitude and linkage of these interactions can be probed in vitro by physical studies. Intrinsic tryptophan fluorescence was used to characterize GalR:D-galactose binding as a function of temperature. The binding appears cooperative, at least at low temperatures, and the estimated van't Hoff enthalpy ( HvH) is -2.5 kcal/mol. Direct calorimetric determination of the thermodynamic parameters for ligand binding to GalR will improve our understanding of the energetics and allosteric control in this system, and of transcriptional regulation in general.