The members of plant metallothionein (MT) subfamily p1 are characterized with the presence
of six Cys at each end of N- and C-terminal of their amino acid sequences which are arranged in
a CXCXXXCXCXXXCXC and CXCXXXCXCXXCXC sequence, respectively. In this study we
evaluated the independence of N-terminal Cys-rich region of a type 1 MT isoform from rice (OsMTI-
1b) in forming metal-thiolate cluster. To this end the N-terminal of OsMTI-1b (N-OsMTI-1b) was
heterologously expressed in Escherichia coli as fusion protein with glutathione-S-transferase (GST).
The E.coli cells expressing GST-N-OsMTI-1b were able to remove Cd2+ and Ni2+ from culture medium.
The recombinant GST-N-OsMTI-1b was purified using affinity chromatography. The UV absorption spectra recorded
after the reconstitution of the apo-protein with Cd2+ and Ni2+ confirmed that GST-N-OsMTI-1b was able to form
complexes with Cd2+ and Ni2+. These results demonstrate the formation of independent metal-thiolate cluster at Nterminal
Cys-rich region of GST-N-OsMTI-1b without participation of C-terminal Cys-rich region.
Keywords: Metallothionein, Metal-thiolate cluster, N-terminal Cys-rich region, OsMTI-1b, Rice.
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