Rakshit D, Vasák M
Institute of Biochemistry, University of Zürich, Switzerland.
J Biol Chem. 1992 Jan 5;267(1):235-8.
Solvent perturbation studies in 100% dimethyl sulfoxide (Me2SO) have been carried out on rabbit liver metallothionein (MT) in an effort to learn more about the factors stabilizing the three-dimensional structure and the mechanism of cluster formation. As indicated by the electronic absorption spectra of Co7-metallothionein, the reconstituted protein preserves its structural integrity in this solvent. Minor spectral differences between water and Me2SO were fully reversible. The titration of apoMT with cobalt(II) in Me2SO, followed by UV-visible-near-infrared electronic absorption, circular dichroism, magnetic circular dichroism, and EPR spectroscopy, indicate that the protein can refold in this solvent. A comparison with the previous titration data in water reveals that the first four titration steps in both solvents are identical, indicating a thermodynamically controlled folding process. However, the reversed order of the cluster completion between Me2SO and water may suggest the involvement of a kinetically controlled folding process in the last three titration steps. A new cluster form developed with approximately nine Co(II) equivalents.
为了更多地了解稳定三维结构的因素以及簇形成的机制，我们对兔肝金属硫蛋白（MT）在100%二甲基亚砜（Me2SO）中进行了溶剂扰动研究。如Co7 - 金属硫蛋白的电子吸收光谱所示，重构后的蛋白质在这种溶剂中保持其结构完整性。水和Me2SO之间的微小光谱差异是完全可逆的。在Me2SO中用钴（II）滴定脱辅基金属硫蛋白，随后进行紫外 - 可见 - 近红外电子吸收、圆二色性、磁圆二色性和电子顺磁共振光谱分析，结果表明该蛋白质可以在这种溶剂中重新折叠。与之前在水中的滴定数据相比，发现在两种溶剂中的前四个滴定步骤是相同的，这表明是一个热力学控制的折叠过程。然而，Me2SO和水之间簇形成完成的顺序相反，这可能表明在最后三个滴定步骤中涉及一个动力学控制的折叠过程。一种新的簇形式由大约九个钴（II）当量形成。
