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PDBsum entry 2kak
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Metal binding protein
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PDB id
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2kak
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References listed in PDB file
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Key reference
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Title
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The beta(e)-Domain of wheat e(c)-1 metallothionein: a metal-Binding domain with a distinctive structure.
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Authors
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E.A.Peroza,
R.Schmucki,
P.Güntert,
E.Freisinger,
O.Zerbe.
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Ref.
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J Mol Biol, 2009,
387,
207-218.
[DOI no: ]
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PubMed id
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Abstract
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Metallothioneins (MTs) are ubiquitous cysteine-rich proteins with a high
affinity for divalent metal ions such as Zn(II), Cu(I), and Cd(II) that are
involved in metal ion homeostasis and detoxification, as well as protection
against reactive oxygen species. Here we show the NMR solution structure of the
beta(E)-domain of the early cysteine-labeled protein (E(c)-1) from wheat
(beta(E)-E(c)-1), which represents the first three-dimensional structure of a
plant MT. The beta(E)-domain comprises the 51 C-terminal residues of E(c)-1 and
exhibits a distinctive unprecedented structure with two separate metal-binding
centers, a mononuclear Zn(II) binding site constituted by two cysteine and two
highly conserved histidine residues as found in certain zinc-finger motifs, and
a cluster formed by three Zn(II) ions coordinated by nine Cys residues that
resembles the cluster in the beta-domain of vertebrate MTs. Cys-metal ion
connectivities were determined by exhaustive structure calculations for all 7560
possible configurations of the three-metal cluster. Backbone dynamics
investigated by (15)N relaxation experiments support the results of the
structure determination in that beta(E)-E(c)-1 is a rigidly folded polypeptide.
To further investigate the influence of metal ion binding on the stability of
the structure, we replaced Zn(II) with Cd(II) ions and examined the effects of
metal ion release on incubation with a metal ion chelator.
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Figure 2.
Fig. 2. [^15N,^1H]-HSQC spectrum of Zn[4]β[E]-E[c]-1
recorded at 600 MHz proton frequency and 300 K.
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Figure 3.
Fig. 3. Backbone presentation of the structure bundle of
Zn[4]β[E]-E[c]-1 in two different views as determined in this
work. His and Cys side chains are additionally shown in red and
blue, respectively, and Zn^II ions are shown as blue spheres.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2009,
387,
207-218)
copyright 2009.
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