The two Caenorhabditis elegans metallothioneins (CeMT-1 and CeMT-2) discriminate between essential zinc and toxic cadmium
The two Caenorhabditis elegans metallothioneins (CeMT-1 and CeMT-2) discriminate between essential zinc and toxic cadmium
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两种秀丽隐杆线虫金属硫蛋白（CeMT-1 和 CeMT-2）可区分必需的锌和有毒的镉
DOI：
10.1111/j.1742-4658.2010.07667.x
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Zeitoun-Ghandour S
中科院分区：
文献类型：
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作者：
Zeitoun-Ghandour S
线虫 优雅线虫表达两种金属硫蛋白：cemt-1和cemt-2，它们被认为是抵御金属毒性的关键分子。在本研究中，这两种异构体都在 试管中表达，无论是在锌(II)还是在镉(II)的存在下。用电喷雾质谱(ESI-MS)和核磁共振谱(NMR)分别测定了金属结合的化学计量比和亲和力。这两种亚型的锌结合能力相同，但镉结合行为不同，与cemt-2的亲和力更高。此外，野生型 线虫、单MT敲除和双MT敲除等位基因分别暴露于锌(340 μm)或镉(25 μm)，以研究其对 体内的影响。锌水平在所有基因敲除菌株中都显著增加，但在cemt-1基因敲除的mtl-1(Tm1770)中最为明显，而镉的积累在cemt-2基因敲除mtl-2(Gk125)和双基因敲除mtl-1；mtl-2(Zs1)中最高。此外，还用X射线吸收精细结构光谱分析了金属的形态。这表明供氧配体在维持锌的生理浓度方面起主导作用，而不受金属硫蛋白状态的影响。相反，镉与硫醇基团配位，野生型和cemt-2基因敲除菌株的镉形态明显不同于cemt-1和双基因敲除菌株。综上所述，并通过一个简单的模型计算，这些发现首次表明，这两个MT亚型在细胞水平上对Cd(II)和Zn(II)具有不同的亲和力，这在蛋白质水平上得到了反映。这表明这两种MT亚型具有不同的 病毒孔。
The nematodeCaenorhabditis elegansexpresses two metallothioneins (MTs), CeMT‐1 and CeMT‐2, that are believed to be key players in the protection against metal toxicity. In this study, both isoforms were expressedin vitroin the presence of either Zn(II) or Cd(II). Metal binding stoichiometries and affinities were determined by ESI‐MS and NMR, respectively. Both isoforms had equal zinc binding ability, but differed in their cadmium binding behaviour, with higher affinity found for CeMT‐2. In addition, wild‐typeC. elegans, single MT knockouts and a double MT knockout allele were exposed to zinc (340 μm) or cadmium (25 μm) to investigate effectsin vivo. Zinc levels were significantly increased in all knockout strains, but were most pronounced in the CeMT‐1 knockout,mtl‐1(tm1770), while cadmium accumulation was highest in the CeMT‐2 knockout,mtl‐2(gk125) and the double knockoutmtl‐1;mtl‐2(zs1). In addition, metal speciation was assessed by X‐ray absorption fine‐structure spectroscopy. This showed that O‐donating, probably phosphate‐rich, ligands play a dominant role in maintaining the physiological concentration of zinc, independently of metallothionein status. In contrast, cadmium was shown to coordinate with thiol groups, and the cadmium speciation of the wild‐type and the CeMT‐2 knockout strain was distinctly different to the CeMT‐1 and double knockouts. Taken together, and supported by a simple model calculation, these findings show for the first time that the two MT isoforms have differential affinities towards Cd(II) and Zn(II) at a cellular level, and this is reflected at the protein level. This suggests that the two MT isoforms have distinctin vivoroles.