PDBsum entry: 1q06

Transcription

PDB-id: 1q06

Biological unit* = asymmetric unit,
as shown
(*as deduced by PQS)

Contents

Description

Header details

Header records

References

PROCHECK

Protein chains

122 a.a. *

126 a.a. *

Metal ions

_AG ×2

Waters ×135

* Residue conservation analysis

Tools

Clefts Calculation

PDB id:

1q06

Name:

Transcription

Title:

Crystal structure of the ag(i) form of e. Coli cuer, a copper efflux regulator

Structure:

Transcriptional regulator cuer. Chain: a, b. Synonym: copper efflux regulator, copper export regulator. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562. Gene: cuer. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Biological unit:

Dimer (from PQS)

UniProt:

Chain A: P0A9G4 (CUER_ECOLI)

Seq:	135 a.a.
Struc:	122 a.a.

Chain B: P0A9G4 (CUER_ECOLI)

Seq:

135 a.a.

Struc:

126 a.a.

Key:	PfamA domain
Secondary structure	CATH domain

Resolution:

2.07Å

R-factor:

0.219

R-free:

0.259

Authors:

A.Changela,K.Chen,Y.Xue,J.Holschen,C.E.Outten, T.V.O'Halloran,A.Mondragon

Key ref:

A.Changela et al. (2003). Molecular basis of metal-ion selectivity and zeptomolar sensitivity by CueR.. Science, 301, 1383-1387. [PubMed id: 12958362] [DOI: 10.1126/science.1085950]

Date:

15-Jul-03

Release date:

16-Sep-03

Related entries:

1q05
the cu(i) form of e. Coli cuer
1q07
the au(i) form of e. Coli cuer

Quick_links

Procheck

Clefts

Surface

Key reference

DOI no: 10.1126/science.1085950

Science 301:1383-1387 (2003)

PubMed id: 12958362

Molecular basis of metal-ion selectivity and zeptomolar sensitivity by CueR.

A.Changela, K.Chen, Y.Xue, J.Holschen, C.E.Outten, T.V.O'Halloran, A.Mondragón.

ABSTRACT

The earliest of a series of copper efflux genes in Escherichia coli are controlled by CueR, a member of the MerR family of transcriptional activators. Thermodynamic calibration of CueR reveals a zeptomolar (10(-21) molar) sensitivity to free Cu+, which is far less than one atom per cell. Atomic details of this extraordinary sensitivity and selectivity for +1transition-metal ions are revealed by comparing the crystal structures of CueR and a Zn2+-sensing homolog, ZntR. An unusual buried metal-receptor site in CueR restricts the metal to a linear, two-coordinate geometry and uses helix-dipole and hydrogen-bonding interactions to enhance metal binding. This binding mode is rare among metalloproteins but well suited for an ultrasensitive genetic switch.

Selected figure(s)

Figure 2.
Fig. 2. (A) Overall structure of the Cu-CueR dimer. The ribbon diagram depicts one monomer in gray and the functional domains in the other monomer in color, with the DNA-binding domain in blue, the dimerization helix in red, and the metal-binding domain in purple. The N-terminal DNA-binding domain consists of two helix-turn-helix motifs and a three-stranded antiparallel ß sheet. The second helix-turn-helix motif of the DNA-binding domain is followed by a five-residue loop connecting to a 10-turn helix. This long helix links the DNA-binding domain to the metal-binding domain and contributes to the bulk of the dimerization interface by forming an antiparallel coiled coil with the equivalent helix of the other monomer. The copper ions are shown as cyan spheres, and the coordinating cysteines, Cys112 and Cys120, are highlighted in ball-and-stick representation. Most of the metal-binding loop of one monomer (residues 115 to 119) and the last eight residues at the C-termini of both monomers are disordered and are not included in the model. (B) A space-filling model of CueR reveals the solvent inaccessibility of the bound metal. The protein is shown in gray and its orientation is similar to that used in (A). The sulfur atoms of the cysteine ligands are colored yellow, and the buried Cu+ ion is depicted in blue.

Figure 3.
Fig. 3. (A) Side-by-side close-up views showing details of the metal-binding regions in CueR and ZntR. The CueR structure reveals a linear Cu+ dithiolate coordination by conserved Cys112 and Cys120. The Cu+ ion is depicted as a cyan sphere, and secondary structural elements are shown in the same color scheme as in Fig. 2A. Other functional groups residing on the metal-binding loop are shown, but do not make any contacts to the metal. Ser77 from the other monomer is oriented away from the metal. A close-up view of the metal-binding region of ZntR is presented in a similar orientation to that of CueR. The domains are shown in the same color scheme used for CueR. The two Zn2^+ ions are depicted as green spheres. Zn1 is coordinated to Cys114 and Cys124 of the metal-binding loop, and to Cys79 from the other monomer. Zn2 is coordinated to Cys115 and His119 of the metal-binding loop and Cys79 of the other monomer. Each Zn2^+ atom is also coordinated by an oxygen atom of a bridging phosphate ion, shown in ball-and-stick representation with the phosphate atom colored magenta. The coordinate-covalent bonds to the metal ions are shown in orange. (B) Schematic diagram detailing various hydrogen-bonding interactions at the CueR metal-binding site. Residues from the metal-binding loop and the first turn of the C-terminal helix are shown in black, and residues from the other monomer are highlighted in red. Hydrogen-bonding interactions (within 3.2 Å for N/O donor/acceptor pairs and 3.8 Å for S-X acceptors) are depicted by dotted lines. S-Cu bonds are shown by bold lines. (C) Close-up view looking down along the helix extending from the C-terminus of the metal-binding loop reveals that Cys120 is centered on the helix and only 2.0 Å away from its N-terminus. Whereas Cys112 and the metal ion also appear to be oriented over the helix dipole, both are distant from the N-terminal end of the helix (approximate distances of Cys112 and the Cu+ ion to the N-terminal end of the helix are 6.5 and 4.0 Å, respectively). Structural elements and bonds are colored using the same scheme as in Fig. 2A, and the metal-binding loop has been omitted for clarity.

The above figures are reprinted by permission from the AAAs: Science (2003, 301, 1383-1387) copyright 2003.

Figures were selected by an automated process.