PDBsum entry 2kak

Metal binding protein

PDB id: 2kak

Contents

Protein chain

53 a.a.

Metals

_ZN ×4

PDB id:

2kak

Name:

Metal binding protein

Title:

Solution structure of the beta-e-domain of wheat ec-1 metallothionein

Structure:

Ec protein i/ii. Chain: a. Fragment: unp residues 31-81. Synonym: zinc metallothionein class ii. Engineered: yes

Source:

Triticum aestivum. Canadian hard winter wheat,common wheat,wheat. Organism_taxid: 4565. Expressed in: escherichia coli. Expression_system_taxid: 562. Expression_system_variant: bl21(de3).

NMR struc:

20 models

Authors:

E.A.Peroza,R.Schmucki,P.Guntert,E.Freisinger,O.Zerbe

Key ref:

E.A.Peroza et al. (2009). The beta(E)-domain of wheat E(c)-1 metallothionein: a metal-binding domain with a distinctive structure. J Mol Biol, 387, 207-218. PubMed id: 19361445 DOI: 10.1016/j.jmb.2009.01.035

Date:

06-Nov-08 Release date: 05-May-09

Protein chain

P30569  (EC1_WHEAT) -  EC protein I/II from Triticum aestivum

Seq: 81 a.a.

Struc: 53 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.jmb.2009.01.035

J Mol Biol 387:207-218 (2009)

PubMed id: 19361445

The beta(E)-domain of wheat E(c)-1 metallothionein: a metal-binding domain with a distinctive structure.

E.A.Peroza, R.Schmucki, P.Güntert, E.Freisinger, O.Zerbe.

ABSTRACT

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.

Selected figure(s)

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.

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.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2009, 387, 207-218) copyright 2009.

Figures were selected by the author.

Author's comment

Structure was solved in absence of explicit metal-cysteine domains