PDBsum entry: 2q0o

Transcription

PDB id: 2q0o

Contents

Protein chains

235 a.a. *

86 a.a. *

Ligands

LAE ×2

Waters ×484

* Residue conservation analysis

PDB id:

2q0o

Name:

Transcription

Title:

Crystal structure of an anti-activation complex in bacterial sensing

Structure:

Probable transcriptional activator protein trar. Chain: a, b. Engineered: yes. Probable transcriptional repressor tram. Chain: c, d. Engineered: yes

Source:

Rhizobium sp.. Organism_taxid: 394. Strain: ngr234. Gene: trar. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008. Gene: tram.

Resolution:

2.00Å R-factor: 0.235 R-free: 0.276

Authors:

G.Chen,P.D.Jeffrey,C.Fuqua,Y.Shi,L.Chen

Key ref:

G.Chen et al. (2007). Structural basis for antiactivation in bacterial quorum sensing. Proc Natl Acad Sci U S A, 104, 16474-16479. PubMed id: 17921255 DOI: 10.1073/pnas.0704843104

Date:

22-May-07 Release date: 25-Sep-07

Protein chains

P55407  (TRAR_RHISN) -  Probable transcriptional activator protein traR

Seq: 236 a.a.

Struc: 235 a.a.

Protein chains

P55408  (TRAM_RHISN) -  Probable transcriptional repressor traM

Seq: 107 a.a.

Struc: 86 a.a.

 Gene Ontology (GO) functional annotation 

• Cellular component: intracellular (1 term)
• Biological process: intracellular signal transduction (7 terms)
• Biochemical function: two-component response regulator activity (4 terms)

DOI no: 10.1073/pnas.0704843104

Proc Natl Acad Sci U S A 104:16474-16479 (2007)

PubMed id: 17921255

Structural basis for antiactivation in bacterial quorum sensing.

G.Chen, P.D.Jeffrey, C.Fuqua, Y.Shi, L.Chen.

ABSTRACT

Bacteria can communicate via diffusible signal molecules they generate and release to coordinate their behavior in response to the environment. Signal molecule concentration is often proportional to bacterial population density, and when this reaches a critical concentration, reflecting a bacterial quorum, specific behaviors including virulence, symbiosis, and horizontal gene transfer are activated. Quorum-sensing regulation in many Gram-negative bacteria involves acylated homoserine lactone signals that are perceived through binding to LuxR-type, acylated-homoserine-lactone-responsive transcription factors. Bacteria of the rhizobial group employ the LuxR-type transcriptional activator TraR in quorum sensing, and its activity is further regulated through interactions with the TraM antiactivator. In this study, we have crystallographically determined the 3D structure of the TraR-TraM antiactivation complex from Rhizobium sp. strain NGR234. Unexpectedly, the antiactivator TraM binds to TraR at a site distinct from its DNA-binding motif and induces an allosteric conformational change in the protein, thereby preventing DNA binding. Structural analysis reveals a highly conserved TraR-TraM interface and suggests a mechanism for antiactivation complex formation. This structure may inform alternative strategies to control quorum-sensing-regulated microbial activity including amelioration of infectious disease and antibiotic resistance. In addition, the structural basis of antiactivation presents a regulatory interaction that provides general insights relevant to the field of transcription regulation and signal transduction.

Selected figure(s)

Figure 1.
Fig. 1. Biochemical characterizations of the TraR[NGR]–TraM[NGR] complex. (A) ITC analysis of the TraR[NGR]–TraM[NGR] interaction. A single binding site was used to fit the data and to derive thermodynamic parameters. (B) AUC sedimentation equilibrium studies on the TraR[NGR]–TraM[NGR] complex. A single species model was used to fit data. Data fitting (Upper) and the fitting residual (Lower) are shown.

Figure 2.
Fig. 2. Overall structure of the TraR[NGR]–TraM[NGR] complex. (A) Structure of tetrameric NGR234 TraR–TraM complex. The TraR[NGR]–TraM[NGR] pair in the closed conformation is colored red and blue, respectively, whereas the other pair in the open conformation is in dark red and dark blue, respectively. The ligand AHL is shown in a ball-and-stick representation. 10, the major TraM-binding site, and 12, the DNA recognition helix, are colored in cyan and orange, respectively. The linker is colored in green. (B) Model of symmetric (TraR[NGR]–TraM[NGR])[2] in solution. The model was generated by applying the C2 rotational symmetry of the NTDs to the closed conformation of dimeric TraR[NGR]–TraM[NGR]. No structural conflicts are observed in the symmetric model. Views of A and B are the same. The figures were generated by using MOLSCRIPT and RASTER 3D (28, 29).

Figures were selected by an automated process.