A glutathione S-transferase from Proteus mirabilis involved in heavy metal resistance and its potential application in removal of Hg~(2+)

摘要

Glutathione S-transferases (GSTs) are a family of multifunctional proteins playing important roles in detoxification of harmful physiological and xenobiotic compounds in organisms. In our study, a gene encoding a GST from Proteus mirabilis strain V7, gst_(pm)-4, was cloned and conditionally expressed in Escherichia coli strain BL21(DE3). The purified Gst_(pm)-4 protein, with an estimated molecular mass of approximately 23 kDa, was able to conjugate l-chloro-2,4-dinitrobenzene and bind to the GSH-affinity matrix. Real-time reverse transcriptase PCR suggested that mRNA level of gst_(pm)-4 was increased in the presence of CdCl_2, CuCl_2, HgCl_2 and PbCl_2, respectively. Correspondingly, overexpression of gst_(pm)-4 in the genetically engineered bacterium Top10/pLacpGst exhibited higher heavy metal resistance compared to the control Top10/pLacP3. Another genetically engineered bacterium Top10/pBATGst, in which the DNA encoding Gst_(pm)-4 protein was fused with the DNA encoding Pfa1-based auto surface display system, was built. Top10/pBATGst could constitutively express the chimeric Gst_(pm)-4 and anchor it onto the cell surface subsequently. Almost 100% of the Hg~(2+) within the range of 0.1-100 nM was adsorbed by Top10/pBATGst, and 80% of the bounded Hg~(2+) could be desorbed from bacterial cells when pH was adjusted to 6.0. Thus, Top10/pBATGst can be potentially used for efficient treatment of Hg~(2+)-contaminated aquatic environment.