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Expression of Rice Metallothionein Isoforms in Escherichia coli Enhances the Accumulation of Trivalent and Hexavalent Chromium

Author(s):

Azar Shahpiri* and Amir Mohammad Rahimi   Pages 1 - 8 ( 8 )

Abstract:


Introduction: Metallothioneins (MTs) are low molecular weight, cysteine-rich and heavy metal-binding proteins involved in heavy metal homeostasis and detoxification in living organisms. Plants have several MT isoforms, which are classi´Čüed into four types based on the arrangement of Cys residues.

Methods: In the present work the engineered E. coli cells which express four different rice MT (OsMT) isoforms were analyzed for the accumulation of two forms of chromium, Cr3+ and Cr6+. Results: The results show that the tolerance of cells expressing OsMT isoforms was higher than that for the control cells when they were grown up in the medium containing Cr(NO3)3.9H2O or Na2CrO4. The cells expressing OsMT1, OsMT2, OsMT3 and OsMT4 give rise to 6.5-, 2.7-, 5.5- and 2.1-fold improvements on the accumulation capacity for Cr3+ and 9-, 3-, 5- and 3- fold Cr6+ respectively in comparison to the control strain. Furthermore the recombinant GST-OsMTs were purified and their binding ability for Cr+3 and Cr+6 were tested in vitro.

Discussion: The data show that the recombinant GST-OsMT1 and GST-OsMT2 were able to bind both Cr3+ and Cr6+, in vitro. However their binding strength was low with respect to previous tested divalent ions like Cd2+.

Keywords:

Chromium , Heterologous expression , Metallothionein , Remediation, Rice

Affiliation:

Department of Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Department of Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111



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