Characterization analysis and heavy metal‐binding properties of CsMTL3 in Escherichia coli

• Published in: FEBS open bio Vol. 8; no. 11; pp. 1820 - 1829
• Main Authors: Xu, Xing, Duan, Ling, Yu, Jingwen, Su, Chenggang, Li, Jinhua, Chen, Dan, Zhang, Xingguo, Song, Hongyuan, Pan, Yu
• Format: Journal Article
• Language: English
• Published: England John Wiley and Sons Inc 01.11.2018
• Subjects: CsMTL3; Escherichia coli; heavy metal tolerance; heavy metal‐binding; metallothionein; Escherichia coli; CsMTL3; heavy metal tolerance; metallothionein; heavy metal‐binding
• ISSN: 2211-5463; 2211-5463
• DOI: 10.1002/2211-5463.12520

Members of the metallothionein (MT) superfamily are involved in coordinating transition metal ions. In plants, MT family members are characterized by their arrangement of Cys residues. In this study, one member of the MT superfamily, CsMTL3, was characterized from a complementary DNA (cDNA) library from young cucumber fruit; CsMTL3 is predicted to encode a 64 amino acid protein with a predicted molecular mass of 6.751 kDa. Phylogenetic analysis identified it as a type 3 family member as the arrangement of N‐terminal Cys residues was different from that of MT‐like 2. Heterologous expression of CsMTL3 in Escherichia coli improved their heavy metal tolerance, particularly to Cd2+ and Cu2+, and led to increased uptake of Cd2+ and Cu2+; increased uptake was also observed for cells expressing Arabidopsis thaliana metallothionein 3 (AtMT3) and phytochelatin‐like (PCL), with greatest uptake in PCL‐expressing cells. These findings demonstrate that CsMTL3 can improve metal tolerance, especially for Cd2+ ions, when heterologously expressed in E. coli, and suggest that the composition and arrangement of N‐terminal Cys residues are associated with binding capacity and preference for different metal ions. Metallothioneins (MTs) are among the most well‐characterized heavy metal‐binding ligands in plants. RT‐qPCR and heterologous expression analysis revealed that CsMTL3 significantly improves heavy metal tolerance, and enhances heavy metal uptake. Our results demonstrate that CsMTL3 is a candidate gene for improving metal tolerance, and provide insights for future studies of the function of CsMTL3 in plants.