Structural highlights
Function[EC1_WHEAT] Binds 5 molecules of zinc. May have a role in Zn(2+) homeostasis during embryogenesis. Publication Abstract from PubMedMetallothioneins (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 beta(E) domain was recently described. Here we present the structure of the N-terminal second domain, gamma-E(c)-1, determined by NMR spectroscopy. The gamma-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)gamma-E(c)-1 clearly shows the presence of a ZnS(4) coordination sphere with average Zn-S distances of 2.33 A. (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 gamma-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 gamma domain and the beta(E) domain within the full-length protein. Protein and metal cluster structure of the wheat metallothionein domain gamma-E(c)-1: the second part of the puzzle.,Loebus J, Peroza EA, Bluthgen N, Fox T, Meyer-Klaucke W, Zerbe O, Freisinger E J Biol Inorg Chem. 2011 Mar 25. PMID:21437709[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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