title: Protein and metal cluster structure of the wheat metallothionein domain γ-E(c)-1: the second part of the puzzle.
abstract: Metallothioneins (MTs) are small cysteine-rich proteins coordinating various transition metal ions, including Zn(II), Cd(II), and Cu(I). MTs are ubiquitously present in all phyla, indicating a successful molecular concept for metal ion binding in all organisms. The plant MT E(c)-1 from Triticum aestivum, common bread wheat, is a Zn(II)-binding protein that comprises two domains and binds up to six metal ions. The structure of the C-terminal four metal ion binding β(E) domain was recently described. Here we present the structure of the N-terminal second domain, γ-E(c)-1, determined by NMR spectroscopy. The γ-E(c)-1 domain enfolds an M (2) (II) Cys(6) cluster and was characterized as part of the full-length Zn(6)E(c)-1 protein as well as in the form of the separately expressed domain, both in the Zn(II)-containing isoform and the Cd(II)-containing isoform. Extended X-ray absorption fine structure analysis of Zn(2)γ-E(c)-1 clearly shows the presence of a ZnS(4) coordination sphere with average Zn-S distances of 2.33 Å. (113)Cd NMR experiments were used to identify the M(II)-Cys connectivity pattern, and revealed two putative metal cluster conformations. In addition, the general metal ion coordination abilities of γ-E(c)-1 were probed with Cd(II) binding experiments as well as by pH titrations of the Zn(II) and Cd(II) forms, the latter suggesting an interaction of the γ domain and the β(E) domain within the full-length protein.
authors: Institute of Inorganic Chemistry, University of Zurich, Switzerland.
authors: Jens
authors: J
authors: Loebus
authors: Estevão A
authors: EA
authors: Peroza
authors: Nancy
authors: N
authors: Blüthgen
authors: Thomas
authors: T
authors: Fox
authors: Wolfram
authors: W
authors: Meyer-Klaucke
authors: Oliver
authors: O
authors: Zerbe
authors: Eva
authors: E
authors: Freisinger
mesh_terms: D000595:Amino Acid Sequence; D002104:Cadmium / Q000378:metabolism; D008668:Metallothionein / Q000737:chemistry* / Q000378:metabolism; D008670:Metals / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D014908:Triticum / Q000737:chemistry* / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D008670:Metals; D010940:Plant Proteins; D002104:Cadmium; D008668:Metallothionein; D015032:Zinc