Domènech Jordi, Tinti Anna, Capdevila Mercè, Atrian Silvia, Torreggiani Armida
Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona (Spain).
Biopolymers. 2007 Jun 15;86(3):240-8. doi: 10.1002/bip.20729.
Zn- and Cd-complexes of Quercus suber metallothionein (QsMT) were obtained by in vivo-synthesis, in order to obtain physiologically representative aggregates, and characterized by spectrometric and spectroscopic methods. The secondary structure elements and the coordination environments of the metal binding sites of the two aggregates were determined, as well as the main metal-containing species formed. The results obtained from the analysis of the Raman and IR spectra reveal that these metal-MT complexes predominantly contain beta-sheet elements (about 60%), whereas they lack alpha-helices. These structural features slightly depend on the divalent metal bound. In particular, Cd(II) binding to QsMT induces a slight increase of the beta-sheet percentage, as well as a decrease in beta-turn elements with respect to Zn(II) binding. Conversely, the in vivo capability of QsMT to inglobe metal and sulfide ions is metal-depending. Spectroscopic vibrational data also confirm the presence of sulfide ligands in the metal clusters of both Zn- and Cd-QsMT, while the participation of the spacer His residue in metal coordination was only found in Cd-QsMT, in agreement with the CD results. Overall data suggest different coordination environments for Zn(II) and Cd(II) ions in QsMT.
通过体内合成获得了栓皮栎金属硫蛋白（QsMT）的锌和镉配合物，以得到具有生理代表性的聚集体，并采用光谱法和波谱法对其进行了表征。确定了两种聚集体的二级结构元件和金属结合位点的配位环境，以及形成的主要含金属物种。拉曼光谱和红外光谱分析结果表明，这些金属-MT配合物主要含有β-折叠元件（约60%），而缺乏α-螺旋。这些结构特征在一定程度上取决于所结合的二价金属。特别是，与QsMT结合的Cd（II）会导致β-折叠百分比略有增加，相对于与Zn（II）结合而言，β-转角元件减少。相反，QsMT在体内包裹金属和硫离子的能力取决于金属。光谱振动数据也证实了在Zn-QsMT和Cd-QsMT的金属簇中均存在硫化物配体，而间隔组氨酸残基参与金属配位仅在Cd-QsMT中被发现，这与圆二色光谱结果一致。总体数据表明QsMT中Zn（II）和Cd（II）离子具有不同的配位环境。
