title: Zn tolerance of novel Colocasia esculenta metallothionein and its domains in Escherichia coli and tobacco.
abstract: Contrary to extensive researches on the roles of metallothioneins (MTs) in metal tolerance of animals, the roles of plant MTs in metal tolerance are largely under investigation. In this study, we evaluated the functional role of type 2 MT from Colocasia esculenta (CeMT2b) in Zn tolerance of tobacco and E. coli cells. Under Zn-stress conditions, transgenic tobacco overexpressing CeMT2b displayed much better seedling growth, a significant decrease in the levels of H(2)O(2) and an increase in Zn accumulation compared with the wild type. Overexpression of CeMT2b in E. coli greatly enhanced Zn tolerance and Zn accumulation under Zn stresses compared with control cells. CeMT2b bound 5.38 ± 0.29 atoms of Zn per protein. To identify a structural domain of CeMT2b for Zn binding, we investigated the growth of E. coli expressing each of the N-terminal, C-terminal, and central linker domains or a CNC motif deletion from the C-terminus of full-length CeMT2b. The results showed that the CNC motif is required for Zn tolerance, and the N-terminal domain is more effective in Zn tolerance than the C-terminal domain. Taken together, our results provide direct evidence for functional contributions of CeMT2b in Zn tolerance of tobacco and E. coli cells.
authors.affiliation: Bio-Energy Research Institute, Chonnam National University, 300 Youngbong-Dong, Buk-Gu, Gwangju, 500-757, Republic of Korea.
authors.forename: Yeon-Ok
authors.initials: YO
authors.lastname: Kim
authors.forename: Yoon Gyo
authors.initials: YG
authors.lastname: Lee
authors.forename: Darshan H
authors.initials: DH
authors.lastname: Patel
authors.forename: Ho Myeong
authors.initials: HM
authors.lastname: Kim
authors.forename: Sung-Ju
authors.initials: SJ
authors.lastname: Ahn
authors.forename: Hyeun-Jong
authors.initials: HJ
authors.lastname: Bae
mesh_terms: D020816:Amino Acid Motifs; D003001:Cloning, Molecular; D031060:Colocasia / Q000235:genetics*; D003470:Culture Media / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D017343:Genes, Plant; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000254:growth & development; D016415:Sequence Alignment; D014026:Nicotiana / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D015032:Zinc / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D003470:Culture Media; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D008668:Metallothionein; D006861:Hydrogen Peroxide; D015032:Zinc