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Abstract：
Cadmium is a non-essential toxic heavy metal for organisms, including plants and cyanobacteria. Cadmium resistance transporters involved in resistance of cells against various toxicants such as drugs and effluxes cytotoxic compounds from cells. However, cadmium resistance-associated protein (CadD) has never been reported from a diazotrophic cyanobacterium Anabaena sp. To test whether the hypothetical protein All3255 of Anabaena sp. PCC7120 a homolog of cadmium resistance-associated protein (CadD) involved in cadmium or heavy metal resistance or not, cloning and heterologous expression analysis of all3255 performed in Escherichia coli BL21 (DE3). Our results revealed that the strain transformed with pGEX-5X-2 + all3255 showed resistant towards not only to cadmium but also other heavy metals such as nickel, copper, zinc, lead and cobalt in addition to arsenic than those of transformed with empty vector (pGEX-5X-2). Furthermore, the results of metal accumulation analysis of these cells unveil a lower accumulation of tested heavy metals in all3255-overexpressing E. coli cells than those transformed with empty vector. This study strongly supports the role of All3255 of Anabaena sp. PCC7120 as a CadD efflux pump of heavy metals in E.coli.
摘要：
镉是生物体非必需的有毒重金属，包括植物和蓝藻.镉抗性转运蛋白参与细胞对各种毒物(如药物和来自细胞的细胞毒性化合物)的抗性。然而,镉抗性相关蛋白（CadD）从未从重氮营养蓝藻鱼卵中报道过。为了测试鱼腥草属的假设蛋白All3255。PCC7120与镉或重金属抗性有关的镉抗性相关蛋白（CadD）的同源物，在大肠杆菌BL21（DE3）中进行的all3255的克隆和异源表达分析。我们的结果表明，用pGEX-5X-2+all3255转化的菌株不仅对镉具有抗性，而且对镍等其他重金属也具有抗性。铜，锌，除砷外的铅和钴比用空载体转化的钴（pGEX-5X-2）。此外，这些细胞的金属积累分析结果显示，在过表达all3255的大肠杆菌细胞中，测试重金属的积累低于用空载体转化的大肠杆菌细胞。这项研究强烈支持鱼腥草属的All3255的作用。PCC7120作为大肠杆菌中重金属的CadD外排泵。
