铜转运蛋白C端金属结合域与Ag^+及Hg^(2+)的相互作用

Interaction of C-Terminal Metal-Binding Domain of Copper Transport Protein with Ag^+ and Hg^(2+)

铜转运蛋白(CTR1)不仅参与铜的细胞摄取,而且在其它重金属离子的摄取过程中也发挥重要作用.本文采用紫外-可见(UV-Vis)光谱,核磁共振(NMR)和质谱(MS)的方法,研究了人源CTR1(hCTR1)的C端金属结合域(C8)与Ag+和Hg2+的相互作用.研究表明,Ag+和Hg2+都能与C8结合,但二者与C8的结合机制明显不同.每个C8分子可以结合两个Ag+离子,但一个Hg2+却可以与两个C8形成桥联.此外,Ag+离子与C8的配位是一个中等速度的交换过程,而Hg2+离子则为快速交换过程.C8的半胱氨酸残基是两种离子的重要结合位点,同时组氨酸残基也参与两种金属离子的配位,其中Ag+优先结合组氨酸,而Hg2+则对半胱氨酸的结合具有显著的优势.虽然HCH基序对C8与金属配位至关重要,一些远端的其它氨基酸也可以参与C8与银离子的配位,这可能与CTR1在摄取Ag+过程中的金属转移机制相关.这些结果为理解hCTR1蛋白摄取重金属离子的作用机制提供了必要的信息.

Copper transport protein （CTR1）, which is essential for copper uptake, also plays an important role in the cellular uptake of other heavy metal ions. In this work, the interactions of the C-terminal metal- binding domain of human CTR1 （C8） with both Ag＊ and Hg2. were studied, using ultraviolet-visible （UV-Vis） spectroscopy, nuclear magnetic resonance （NMR） spectroscopy, and mass spectrometry （MS）. The results showed that Ag＊ and Hg2. bind to C8 by different binding modes. Each C8 binds to two Ag＋, whereas one Hg2＋ crosslinks two C8 units. In addition, the coordination of Ag＋ to C8 has an intermediate exchange rate, whereas the binding of Hg2. to C8 has a fast exchange rate. The cysteine residue of C8 is one of the most important binding sites for both Ag＋ and Hg2＋. However, histidine residues are also involved in the metal- binding process. Ag＊ binds histidine preferentially, whereas Hg2＋ prefers to bind to cysteine residues. Although the HCH motif of C8 is crucial for metal binding, some other residues can also participate in the binding of Ag＊. These residues may be involved in the metal-transfer process in the cellular uptake ofAg＋ by CTRI. These results provide important information for a better understanding of the mechanism of cellular uptake of metal ions by CTR1.