Bofill R, Palacios O, Capdevila M, Cols N, González-Duarte R, Atrian S, González-Duarte P
Departament de Química, Facultat de Ciencies, Universitat Autònoma de Barcelona, Spain.
J Inorg Biochem. 1999 Jan-Feb;73(1-2):57-64. doi: 10.1016/S0162-0134(98)10091-0.
The copper(I) and silver(I) binding properties of the beta fragment of recombinant mouse metallothionein I have been studied by electronic absorption and circular dichroism spectroscopy. When possible, the stoichiometry of the species formed was confirmed by electrospray mass spectrometry. The behaviour observed differs from that reported for the native protein. Titration of either Zn3-beta MT at pH 7 or apo-beta MT at pH 3 with Cu+ leads to the formation of species having the same stoichiometry and structure: Cu6-beta MT, Cu7-beta MT and Cu10-beta MT. In the first stage of the titration of Zn3-beta MT with Cu+ at pH 7 one additional species of formula Cu4Zn1-beta MT was detected. In contrast, the titration of Zn3-beta MT at pH 7.5 and of apo-beta MT at pH 2.5 with Ag+ proceeds through different reaction pathways, affording ZnxAg3-beta MT, Ag6-beta MT and Ag9-beta MT or Ag3-beta MT, Ag6-beta MT and Ag9-beta MT, respectively. The CD envelope corresponding to species with the same stoichiometric ratio, Ag6-beta MT and Ag9-beta MT, indicates that they have a different structure at each pH value. On the basis of the differences observed, the postulated similarity between copper and silver binding to metallothionein may be questioned.
通过电子吸收光谱和圆二色光谱研究了重组小鼠金属硫蛋白I的β片段与铜（I）和银（I）的结合特性。在可能的情况下，用电喷雾质谱法确定了所形成物种的化学计量。观察到的行为与天然蛋白质的报道不同。在pH 7下用Cu⁺滴定Zn₃-βMT或在pH 3下滴定脱辅基-βMT，会形成具有相同化学计量和结构的物种：Cu₆-βMT、Cu₇-βMT和Cu₁₀-βMT。在pH 7下用Cu⁺滴定Zn₃-βMT的第一阶段，检测到一种额外的化学式为Cu₄Zn₁-βMT的物种。相比之下，在pH 7.5下用Ag⁺滴定Zn₃-βMT和在pH 2.5下滴定脱辅基-βMT通过不同的反应途径进行，分别得到ZnₓAg₃-βMT、Ag₆-βMT和Ag₉-βMT或Ag₃-βMT、Ag₆-βMT和Ag₉-βMT。对应于具有相同化学计量比的物种Ag₆-βMT和Ag₉-βMT的CD包络表明，它们在每个pH值下具有不同的结构。基于观察到的差异，可能会质疑铜和银与金属硫蛋白结合之间假定的相似性。
