Bioaccumulation of heavy metals in Escherichia coli expressing an inducible synthetic human metallothionein gene

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Abstract

A synthetic DNA coding for human hepatic metallothionein (HMT), fraction MT-2, has been cloned in the plasmid vector pING 1 and expressed in E. coli. Upon induction with arabinose, an araB′-HMT fusion protein is synthesized. The fusion protein is produced to a level of approximately 8% of the total protein in E. coli, with an apparent half-life of 50 min. Without arabinose, no fusion protein is expressed, demonstrating that the expression system is tightly regulated. In the presence of 109Cd, the fusion protein binds the metal ion in vitro. Concurrently, a direct correlation is found between the expression in E. coli of the araB′-HMT fusion protein which binds Cd2+ in vitro and the bioaccumulation of Cd2+ in vivo. The bioaccumulation of Cu+ in E. coli, when the fusion protein is produced, has also been established.

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