PDBsum entry 2osv

Metal transport

PDB id: 2osv

Contents

Protein chains

262 a.a. *

Metals

_ZN ×2

Waters ×596

* Residue conservation analysis

PDB id:

2osv

Name:

Metal transport

Title:

Crystal structure of znua from e. Coli

Structure:

High-affinity zinc uptake system protein znua. Chain: a, b. Fragment: active form (n-terminal signal peptide cleaved)

Source:

Escherichia coli. Organism_taxid: 562. Strain: bl21 star

Resolution:

1.75Å R-factor: 0.175 R-free: 0.216

Authors:

H.Li,G.Jogl

Key ref:

H.Li and G.Jogl (2007). Crystal Structure of the Zinc-binding Transport Protein ZnuA from Escherichia coli Reveals an Unexpected Variation in Metal Coordination. J Mol Biol, 368, 1358-1366. PubMed id: 17399739 DOI: 10.1016/j.jmb.2007.02.107

Date:

06-Feb-07 Release date: 17-Apr-07

Protein chains

P39172  (ZNUA_ECOLI) -  High-affinity zinc uptake system protein ZnuA from Escherichia coli (strain K12)

Seq: 310 a.a.

Struc: 262 a.a.

DOI no: 10.1016/j.jmb.2007.02.107

J Mol Biol 368:1358-1366 (2007)

PubMed id: 17399739

Crystal Structure of the Zinc-binding Transport Protein ZnuA from Escherichia coli Reveals an Unexpected Variation in Metal Coordination.

H.Li, G.Jogl.

ABSTRACT

Bacterial ATP-binding cassette transport systems for high-affinity uptake of zinc and manganese use a cluster 9 solute-binding protein. Structures of four cluster 9 transport proteins have been determined previously. However, the structural determinants for discrimination between zinc and manganese remain under discussion. To further investigate the variability of metal binding sites in bacterial transporters, we have determined the structure of the zinc-bound transport protein ZnuA from Escherichia coli to 1.75 A resolution. The overall structure of ZnuA is similar to other solute-binding transporters. A scaffolding alpha-helix forms the backbone for two structurally related globular domains. The metal-binding site is located at the domain interface. The bound zinc ion is coordinated by three histidine residues (His78, His161 and His225) and one glutamate residue (Glu77). The functional role of Glu77 for metal binding is unexpected, because this residue is not conserved in previously determined structures of zinc and manganese-specific transport proteins. The observed metal coordination by four protein residues differs significantly from the zinc-binding site in the ZnuA transporter from Synechocystis 6803, which binds zinc via three histidine residues. In addition, the E. coli ZnuA structure reveals the presence of a disulfide bond in the C-terminal globular domain that is not present in previously determined cluster 9 transport protein structures.

Selected figure(s)

Figure 1.
Figure 1. Structure of ZnuA. (a) Schematic representation of the structure of ZnuA. Metal-coordinating residues are shown as sticks, the zinc ion is shown as purple sphere. The position of the disordered loop between residues 135 and 157 is indicated by a black line. (b) Final 2F[o–]F[c] electron density map (contoured at 1σ) for residues in the active site region is shown in orange and grey. The anomalous difference Fourier map for data collected at the zinc peak wavelength is shown at a 5σ contour level in dark blue.

Figure 2.
Figure 2. The ZnuA metal-binding site. (a) Stereo representation of the ZnuA metal-binding site. Residues in the first and second coordination shell and the disulfide bond-forming cysteine residues are shown in orange sticks. The zinc ion is shown as purple sphere. Hydrophobic residues surrounding the metal-binding site are shown in grey sticks. (b) Close-up view of the metal-binding site. The interatomic distances between coordinating residues and solvent water molecules are indicated.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2007, 368, 1358-1366) copyright 2007.

Figures were selected by the author.