THERMODYNAMIC MODEL FOR LIGAND-INDUCED BIPHASIC PROTEIN DENATURATION

根据实验数据(Vox Sang.47、7-18(1984)和J.Biol。 化学263,15392-15399(1988年)]，源于热诱导 人血清白蛋白的变性研究，我们得出结论：配体诱导 蛋白质的两相变性，与蛋白质无关 如果蛋白质与配基的亲和力强，就会出现结构域亚结构 是足够大的，如果最初蛋白质是配基亚饱和的。 近似计算表明，这样的描述可以解释 这些观察结果(第42届量热会议(1987年)摘要)。 我们开发了一个严格的热力学模型，它包含了 配体结合对去折叠转变温度的影响 并证明了对一种蛋白质的计算 亲和力常数有三个不同值的单个结合位点 可以再现观察到的白蛋白变性的显著特征 在存在低、中、高亲和力配体的情况下[J.Biol. 化学。265,50555059(1990年))。目前，我们正在进行更详细的工作 白蛋白的计算，利用文献中的结合数据 为了证明热力学模型的计算结果 变性轮廓与实验观察到的相似。在……里面 此外，我们计划用配体诱导的双相来说明这一点 变性，对变性的贡献由不同的 因此，天然蛋白质种类通常不是双态性质 指出标准的反卷积程序将产生一个基础 一组没有物理意义的本构吸热曲线。此外，a 对双峰起源的理论研究表明， 多相(即三相等)可以发生变性，并揭示出 造成这一现象的因素。

On the basis of experimental data (Vox Sang. 47, 7-18 (1984) and J. Biol. Chem 263, 15392-15399 (1988)], which derive from thermally induced denaturation studies of human albumin, we concluded that ligand-induced biphasic denaturation of the protein, which does not relate to protein domain substructure can occur if the affinity of the protein for the ligand is great enough and if initially the protein is subsaturated with ligand. Approximate calculations indicated that such a description can account for these observations (Abstracts of the 42nd Calorimetry Conference (1987)]. We have developed a rigorous thermodynamic model, which incorporates the effects of ligand binding on the transition temperature for the unfolding of the protein and have demonstrated that a computation for a protein with a single binding site with three different values for the affinity constant can reproduce the salient features of the observed denaturation of albumin in the presence of low, intermediate, and high affinity ligands [J. Biol. Chem. 265, 50555059 (1990)). Currently we are carrying out more detailed calculations for albumin, utilizing binding data in the literature, in order to demonstrate that the thermodynamic model results in computed denaturation profiles that closely mimic those observed experimentally. In addition, we plan to illustrate that with ligand-induced biphasic denaturation, contributions to the denaturation profile by the different native protein species are in general not of a two-state nature thereby indicating that standard deconvolution procedures would result in a basis set of constitutive endotherms devoid of physical meaning. Furthermore, a theoretical investigation of the origins of bimodality demonstrates that multiphasic (i.e., triphasic etc.) denaturation can occur and reveals the factors responsible for this phenomenon.