Mercury superfamily proteins, i.e. inner membrane-spanning proteins (MerC, MerE, MerF and MerT) and a periplasmic mercury-binding protein (MerP), transport mercury into the cytoplasm. A previous study demonstrated that a Mer transporter homolog exhibits cadmium transport activity; based on this, the present study aimed to evaluate the cadmium transport activity of MerC, MerE, MerF and MerT and the effects of MerP co-expression in Escherichia coli. Bacteria expressing MerC, MerE, MerF or MerT without MerP were more sensitive to cadmium and significantly absorbed more cadmium than did the control strain. Expression of MerP in combination with MerC, MerE, MerF or MerT increased the bacterial sensitivity to cadmium and cadmium accumulation compared to a single expression of MerC, MerE, MerF or MerT. Cadmium uptake mediated by MerC, MerE, MerF or MerT was inhibited under cold or acidic conditions. These findings suggest that MerC, MerE, MerF and MerT are broad-spectrum heavy metal transporters that mediate both mercury and cadmium transport into cells and that MerP accelerates the cadmium transport ability of MerC, MerE, MerF and MerT.

中文翻译：

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四种汞转运蛋白（MerC，MerE，MerF和MerT）的镉转运活性以及周质汞结合蛋白MerP对依赖于Mer的镉吸收的影响

汞超家族蛋白，即内跨膜蛋白（MerC，MerE，MerF和MerT）和周质汞结合蛋白（MerP），将汞运输到细胞质中。先前的研究表明，Mer转运蛋白同系物具有镉转运活性。基于此，本研究旨在评估MerC，MerE，MerF和MerT的镉转运活性以及MerP共表达在大肠杆菌中的作用。表达MerC，MerE，MerF或不含MerP的MerT的细菌比对照菌株对镉更敏感，并吸收了更多的镉。与MerC，MerE，MerF或MerT的单表达相比，与MerC，MerE，MerF或MerT结合使用MerP的表达增加了细菌对镉和镉积累的敏感性。在寒冷或酸性条件下，由MerC，MerE，MerF或MerT介导的镉吸收受到抑制。这些发现表明，MerC，MerE，MerF和MerT是广谱重金属转运体，可介导汞和镉向细胞内的转运，并且MerP加快了MerC，MerE，MerF和MerT的镉转运能力。