Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 17A, 43124 Parma, Italy.
Inorg Chem. 2020 Dec 7;59(23):16988-16997. doi: 10.1021/acs.inorgchem.0c02171. Epub 2020 Nov 18.
Metallothioneins (MTs) are a large superfamily of ubiquitous cysteine-rich metalloproteins with main functions in metal ion homeostasis and detoxification. Neclu_MT1 is a metallothionein from the aquatic fungus and so far the only known MT that is solely induced by Cd but not by Zn or copper ions. In addition to eight cysteine residues, Neclu_MT1 also contains a less common single C-terminal histidine residue. To better understand the role of this histidine residue in metal ion binding, for the first time, potentiometric pH titrations are applied, revealing insights into the protonation and metal ion binding processes. Additional studies with absorption and NMR spectroscopy complement the finding that while the histidine residue is not crucial for the overall metal binding capacity, it does serve as a ligand in the Zn but not in the Cd form of the protein.
金属硫蛋白（MTs）是一类广泛存在的富含半胱氨酸的金属结合蛋白超家族，主要功能是维持金属离子平衡和解毒。Neclu_MT1 是一种水生真菌中的金属硫蛋白，到目前为止，它是唯一已知的仅由 Cd 而非 Zn 或铜离子诱导的 MT。除了八个半胱氨酸残基外，Neclu_MT1 还含有一个不太常见的单个 C 末端组氨酸残基。为了更好地了解该组氨酸残基在金属离子结合中的作用，首次应用了电位 pH 滴定法，揭示了质子化和金属离子结合过程的见解。吸收和 NMR 光谱学的进一步研究补充了以下发现：虽然该组氨酸残基对于整体金属结合能力并非关键，但它确实是蛋白质 Zn 形式（而非 Cd 形式）的配体。
