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Protein and metal cluster structure of the wheat metallothionein domain γ-Ec-1: the second part of the puzzle

Loebus, Jens ; Peroza, Estevão ; Blüthgen, Nancy ; Fox, Thomas ; Meyer-Klaucke, Wolfram ; Zerbe, Oliver ; Freisinger, Eva

In: JBIC Journal of Biological Inorganic Chemistry, 2011, vol. 16, no. 5, p. 683-694

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    Title
    • Protein and metal cluster structure of the wheat metallothionein domain γ-Ec-1: the second part of the puzzle
    Author
    • Loebus, Jens. Institute of Inorganic Chemistry, University of Zurich, 8057, Zurich, Switzerland
    • Peroza, Estevão. Institute of Inorganic Chemistry, University of Zurich, 8057, Zurich, Switzerland
    • Blüthgen, Nancy. Institute of Inorganic Chemistry, University of Zurich, 8057, Zurich, Switzerland
    • Fox, Thomas. Institute of Inorganic Chemistry, University of Zurich, 8057, Zurich, Switzerland
    • Meyer-Klaucke, Wolfram. European Molecular Biology Laboratory (EMBL), Outstation Hamburg at Deutsches Elektronen-Synchrotron (DESY), 22603, Hamburg, Germany
    • Zerbe, Oliver. Institute of Organic Chemistry, University of Zurich, 8057, Zurich, Switzerland
    • Freisinger, Eva. Institute of Inorganic Chemistry, University of Zurich, 8057, Zurich, Switzerland
    Document Type
    • Postprint
    Language
    • English
    Published in
    • JBIC Journal of Biological Inorganic Chemistry, 2011, vol. 16, no. 5, p. 683-694. Springer-Verlag
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:320005
    Summary
    Metallothioneins (MTs) are small cysteine-rich proteins coordinating various transition metal ions, including ZnII, CdII, and CuI. MTs are ubiquitously present in all phyla, indicating a successful molecular concept for metal ion binding in all organisms. The plant MT Ec-1 from Triticum aestivum, common bread wheat, is a ZnII-binding protein that comprises two domains and binds up to six metal ions. The structure of the C-terminal four metal ion binding βEdomain was recently described. Here we present the structure of the N-terminal second domain, γ-Ec-1, determined by NMR spectroscopy. The γ-Ec-1 domain enfolds an M 2 II Cys6 cluster and was characterized as part of the full-length Zn6Ec-1 protein as well as in the form of the separately expressed domain, both in the ZnII-containing isoform and the CdII-containing isoform. Extended X-ray absorption fine structure analysis of Zn2γ-Ec-1 clearly shows the presence of a ZnS4 coordination sphere with average Zn-S distances of 2.33Å. 113CdNMR experiments were used to identify the MII-Cys connectivity pattern, and revealed two putative metal cluster conformations. In addition, the general metal ion coordination abilities of γ-Ec-1 were probed with CdII binding experiments as well as by pH titrations of the ZnII and CdII forms, the latter suggesting an interaction of the γdomain and the βEdomain within the full-length protein