LOW-TEMPERATURE UNFOLDING OF A MUTANT OF PHAGE-T4 LYSOZYME .1. EQUILIBRIUM STUDIES
LOW-TEMPERATURE UNFOLDING OF A MUTANT OF PHAGE-T4 LYSOZYME .1. EQUILIBRIUM STUDIES
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DOI：
10.1021/bi00428a041
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发表时间：
1989-01-24
期刊：
影响因子：
2.9
通讯作者：
SCHELLMAN, JA
中科院分区：
文献类型：
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作者：
CHEN, BL;SCHELLMAN, JA
噬菌体T4溶菌酶的突变蛋白I3C-C97/C54T不含巯基，在第3位和第97位之间有一个基因工程的二硫键(Perry和Wetzel，1986)。该蛋白在12℃时具有最大的稳定性。C，并在28℃和-3℃下进行可逆的高低温熔融。C，分别在这种介质中。在包括熔融转变的温度范围内，研究了蛋白质稳定的自由能。稳定性曲线在整个范围内符合恒定的ΔCp模型，允许异常完整地确定蛋白质的热力学参数，并证明蛋白质的低温展开形式可以被解释为高温展开形式的恒定的ΔCp的外推。去折叠自由能在实验误差范围内是胍浓度的线性函数，这使得我们可以粗略地估计蛋白质在低温下的稳定性，以及去折叠蛋白质与氯化胍的不同相互作用。这些平衡研究为解释下文(Chen等人，1989)中报告的动力学研究提供了基础。
The mutant protein I3C-C97/C54T of phage T4 lysozyme is free of sulfhydryl groups and has a genetically engineered disulfide bridge between positions 3 and 97 (Perry and Wetzel, 1986). This protein has a maximum stability at 12.degree. C in 3 M guanidinium chloride and undergoes reversible high- and low-temperature melting at 28 and -3.degree. C, respectively, in this medium. The free energy of stabilization of the protein has been studied over a range of temperature that includes both melting transitions. The stability curve fits a constant .DELTA.Cp model over the entire range, permitting an unusually complete determination of the thermodynamic parameters of the protein and demonstrating that the low-temperature unfolded form of the protein may be interpreted as an extrapolation with constant .DELTA.Cp of the high-temperature unfolded form. The free energy of unfolding is a linear function of guanidinium concentration within experimental error which permits a rough estimate of the stability of the protein at low temperatures and of the differential interaction of the unfolded protein with guanidinium chloride. These equilibrium studies provide a basis for the interpretation of the kinetic studies reported in the following paper (Chen et al., 1989).