Enhanced arsenic accumulation by engineered yeast cells expressing Arabidopsis thaliana phytochelatin synthase
Enhanced arsenic accumulation by engineered yeast cells expressing Arabidopsis thaliana phytochelatin synthase
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DOI：
10.1002/bit.21577
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发表时间：
2008-02
影响因子：
3.8
通讯作者：
Shailendra Singh;Wonkyu Lee;Nancy A Dasilva;A. Mulchandani;Wilfred Chen
中科院分区：
文献类型：
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作者：
Shailendra Singh;Wonkyu Lee;Nancy A Dasilva;A. Mulchandani;Wilfred Chen
植物螯合素 (PC) 是天然存在的肽，对包括砷 (As) 在内的多种重金属具有高度结合能力。 PC 由植物螯合素合酶酶促合成，并含有以甘氨酸残基封端的 (γ-Glu-Cys)n 部分，这使得它们具有相对的蛋白水解抗性。在本研究中，通过在酿酒酵母中表达拟南芥植物螯合素合酶 (AtPCS) 来引入 PC，以增强 As 的积累和去除。在广泛的 As 浓度范围内，酵母中 PC 的产生导致 As 积累量比对照菌株高六倍。对于高砷浓度，PC的产生导致PC前体如谷胱甘肽（GSH）和γ-谷氨酰半胱氨酸（γ-EC）的水平大幅下降。发现表达 AtPCS 的野生型菌株和缺乏砷外排系统的表达 AtPCS 的 acr3Δ 菌株之间的 As(III) 积累水平相似，表明砷的吸收可能受到限制。砷和 PC2 (n = 2) 水平之间大约 1:3 的化学计量比（与 1:2 的理论值相比）进一步支持了这一点，表明细胞内 PC 的可用性过剩。然而，在较低的 As(III) 浓度下，PC 产量变得有限，并且对于缺乏外排系统的菌株观察到对砷积累的累加效应。更重要的是，即使是在富含 Zn2+ 的培养基中预培养的表达 AtPCS 的静息细胞，也显示出 PC 的产生以及比对照菌株高两倍的砷去除率。这些结果开辟了使用表达 AtPCS 的细胞作为廉价吸附剂去除有毒砷的可能性。生物技术。生物工程。 2008；99：333-340。 © 2007 Wiley 期刊公司。
Phytochelatins (PCs) are naturally occurring peptides with high‐binding capabilities for a wide range of heavy metals including arsenic (As). PCs are enzymatically synthesized by phytochelatin synthases and contain a (γ‐Glu‐Cys)n moiety terminated by a Gly residue that makes them relatively proteolysis resistant. In this study, PCs were introduced by expressing Arabidopsis thaliana Phytochelatin Synthase (AtPCS) in the yeast Saccharomyces cerevisiae for enhanced As accumulation and removal. PCs production in yeast resulted in six times higher As accumulation as compared to the control strain under a wide range of As concentrations. For the high‐arsenic concentration, PCs production led to a substantial decrease in levels of PC precursors such as glutathione (GSH) and γ‐glutamyl cysteine (γ‐EC). The levels of As(III) accumulation were found to be similar between AtPCS‐expressing wild type strain and AtPCS‐expressing acr3Δ strain lacking the arsenic efflux system, suggesting that the arsenic uptake may become limiting. This is further supported by the roughly 1:3 stoichiometric ratio between arsenic and PC2 (n = 2) level (comparing with a theoretical value of 1:2), indicating an excess availability of PCs inside the cells. However, at lower As(III) concentration, PC production became limiting and an additive effect on arsenic accumulation was observed for strain lacking the efflux system. More importantly, even resting cells expressing AtPCS pre‐cultured in Zn2+ enriched media showed PCs production and two times higher arsenic removal than the control strain. These results open up the possibility of using cells expressing AtPCS as an inexpensive sorbent for the removal of toxic arsenic. Biotechnol. Bioeng. 2008;99: 333–340. © 2007 Wiley Periodicals, Inc.