Kuroda Kouichi, Ebisutani Kazuki, Iida Katsuya, Nishitani Takashi, Ueda Mitsuyoshi
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Biomolecules. 2014 Apr 11;4(2):390-401. doi: 10.3390/biom4020390.
Uranium is one of the most important metal resources, and the technology for the recovery of uranyl ions (UO22+) from aqueous solutions is required to ensure a semi-permanent supply of uranium. The NikR protein is a Ni2+-dependent transcriptional repressor of the nickel-ion uptake system in Escherichia coli, but its mutant protein (NikRm) is able to selectively bind uranyl ions in the interface of the two monomers. In this study, NikRm protein with ability to adsorb uranyl ions was displayed on the cell surface of Saccharomyces cerevisiae. To perform the binding of metal ions in the interface of the two monomers, two metal-binding domains (MBDs) of NikRm were tandemly fused via linker peptides and displayed on the yeast cell surface by fusion with the cell wall-anchoring domain of yeast α-agglutinin. The NikRm-MBD-displaying yeast cells with particular linker lengths showed the enhanced adsorption of uranyl ions in comparison to the control strain. By treating cells with citrate buffer (pH 4.3), the uranyl ions adsorbed on the cell surface were recovered. Our results indicate that the adsorption system by yeast cells displaying tandemly fused MBDs of NikRm is effective for simple and concentrated recovery of uranyl ions, as well as adsorption of uranyl ions.
铀是最重要的金属资源之一，从水溶液中回收铀酰离子（UO22+）的技术对于确保铀的半永久性供应至关重要。NikR蛋白是大肠杆菌中镍离子摄取系统的一种Ni2+依赖性转录阻遏物，但其突变蛋白（NikRm）能够在两个单体的界面处选择性地结合铀酰离子。在本研究中，具有吸附铀酰离子能力的NikRm蛋白展示在酿酒酵母的细胞表面。为了在两个单体的界面处进行金属离子结合，NikRm的两个金属结合结构域（MBD）通过连接肽串联融合，并通过与酵母α-凝集素的细胞壁锚定结构域融合展示在酵母细胞表面。与对照菌株相比，具有特定连接长度的展示NikRm-MBD的酵母细胞对铀酰离子的吸附增强。通过用柠檬酸盐缓冲液（pH 4.3）处理细胞，回收吸附在细胞表面的铀酰离子。我们的结果表明，展示串联融合的NikRm MBD的酵母细胞吸附系统对于铀酰离子的简单浓缩回收以及铀酰离子的吸附是有效的。
