We focused on the application of mass spectrometry and electrochemical methods combined with a chemometric analysis for the characterization of partially metallothionein-3 species. The results showed decreased Cat1 and Cat2 signals for the Zn(II)-loaded MT3 species with respect to the metal-free protein, which might be explained by the arrangement of tetrahedral metal-thiolate coordination environments and the formation of metal clusters. Moreover, there was a decrease in the Cat1 and Cat2 signals, and a plateau was reached with 4-5 Zn(II) ions that corresponded to the formation of the C-terminal α-domain. Regarding the Zn7-xMT3 complexes, we observed three different electrochemical behaviours for the Zn1-2MT3, Zn3-6MT3 and Zn7MT3 species. The difference for Zn1-2MT3 might be explained by the formation of independent ZnS4 cores in this stage that differ with respect to the formation of ZnxCysy clusters with an increased Zn(II) loading. The binding of the third Zn(II) ion to MT3 resulted in high sample heterogeneity due the co-existence of Zn3-6MT3. Finally, the Zn7MT3 protein showed a third type of behaviour. The fact that there were no free Cys residues might explain this phenomenon. Thus, this research identifies the major proteins responsible for zinc buffering in the cell.

中文翻译：

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化学和自由伏安和Zn（II）负载金属硫蛋白3状态的伏安分析。

我们专注于质谱和电化学方法结合化学计量学分析表征部分金属硫蛋白3物种的应用。结果表明，相对于不含金属的蛋白质，Zn（II）负载的MT3物种的Cat1和Cat2信号减少，这可能是由四面体金属-硫醇盐配位环境的排列和金属簇的形成所致。此外，Cat1和Cat2信号减少，并且达到了4-5个Zn（II）离子的平稳状态，这对应于C端α域的形成。关于Zn7-xMT3配合物，我们观察到Zn1-2MT3，Zn3-6MT3和Zn7MT3物种的三种不同的电化学行为。Zn1-2MT3的差异可以通过在此阶段形成独立的ZnS4核来解释，这些核心在形成Zn（II）负荷增加的ZnxCysy团簇方面有所不同。第三个Zn（II）离子与MT3的结合由于Zn3-6MT3的共存而导致高样品异质性。最后，Zn7MT3蛋白表现出第三种行为。没有游离的Cys残基这一事实可能解释了这种现象。因此，这项研究确定了负责锌在细胞中缓冲的主要蛋白质。没有游离的Cys残基这一事实可能解释了这种现象。因此，这项研究确定了负责锌在细胞中缓冲的主要蛋白质。没有游离的半胱氨酸残基这一事实可能解释了这种现象。因此，这项研究确定了负责锌在细胞中缓冲的主要蛋白质。