Cadmium toxicity in glutathione mutants of Escherichia coli
Cadmium toxicity in glutathione mutants of Escherichia coli
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DOI：
10.1128/jb.00272-08
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发表时间：
2008-08-01
影响因子：
3.2
通讯作者：
Nies, Dietrich H.
中科院分区：
文献类型：
--
作者：
Helbig, Kerstin;Grosse, Cornelia;Nies, Dietrich H.
Cd2+对含硫化合物的亲和力高于对氮和氧的亲和力，这使得理论上认为镉毒性主要是由于Cd2+与硫化物、巯基和富硫络合物的结合，而不是由于Cd2+取代了富氮含氧生物化合物的过渡金属阳离子。这一假设通过大肠杆菌对合成谷胱甘肽（GSH，野生型）、γ -谷氨酰半胱氨酸（Delta gshB突变体）或两种细胞硫醇（Delta gshA突变体）的细胞进行全局转录组分析得到验证。结果数据，其中一些通过定量逆转录- pcr验证，使用KEGG（京都基因和基因组百科全书）同源系统进行分类，该系统根据各自产物的细胞功能对基因进行分层分组。三种菌株的主要区别在于色氨酸的生物合成，在镉休克时，色氨酸的生物合成在野生型细胞中上调，在δ gshA细胞中强烈上调，而在含有γ -谷氨酰半胱氨酸而不是GSH的δ gshB细胞中抑制。然而，总的来说，所有三种大肠杆菌菌株对镉休克的反应相似，与蛋白质、二硫键和氧化损伤修复相关的基因上调；半胱氨酸和铁硫簇生物合成；含有敏感铁硫团簇的蛋白质的产生；铁的储存；以及Cd2+的外排解毒。一般的节能途径和铁摄取下调。这些发现表明Cd2+的毒性作用确实是由金属阳离子与硫的结合引起的，从而支持了所测试的假设。
The higher affinity of Cd2+ for sulfur compounds than for nitrogen and oxygen led to the theoretical consideration that cadmium toxicity should result mainly from the binding of Cd2+ to sulfide, thiol groups, and sulfur-rich complex compounds rather than from Cd2+ replacement of transition-metal cations from nitrogenor oxygen-rich biological compounds. This hypothesis was tested by using Escherichia coli for a global transcriptome analysis of cells synthesizing glutathione (GSH; wild type), gamma-glutamylcysteine (Delta gshB mutant), or neither of the two cellular thiols (Delta gshA mutant). The resulting data, some of which were validated by quantitative reverse transcription-PCR, were sorted using the KEGG (Kyoto Encyclopedia of Genes and Genomes) orthology system, which groups genes hierarchically with respect to the cellular functions of their respective products. The main difference among the three strains concerned tryptophan biosynthesis, which was up-regulated in wild-type cells upon cadmium shock and strongly up-regulated in Delta gshA cells but repressed in Delta gshB cells containing gamma-glutamylcysteine instead of GSH. Overall, however, all three E. coli strains responded to cadmium shock similarly, with the up-regulation of genes involved in protein, disulfide bond, and oxidative damage repair; cysteine and iron-sulfur cluster biosynthesis; the production of proteins containing sensitive iron-sulfur clusters; the storage of iron; and the detoxification of Cd2+ by efflux. General energy conservation pathways and iron uptake were down-regulated. These findings indicated that the toxic action of Cd2+ indeed results from the binding of the metal cation to sulfur, lending support to the hypothesis tested.