PDBsum entry 2uxh

Transcription

PDB id: 2uxh

Contents

Protein chains

206 a.a. *

Ligands

QUE ×2

Waters ×191

* Residue conservation analysis

PDB id:

2uxh

Name:

Transcription

Title:

Ttgr in complex with quercetin

Structure:

Hth-type transcriptional regulator ttgr. Chain: a, b. Synonym: toluene efflux pump ttgabc operon repressor, transcriptional repressor. Engineered: yes

Source:

Pseudomonas putida. Organism_taxid: 303. Expressed in: escherichia coli. Expression_system_taxid: 83333. Expression_system_cell_line: b834.

Resolution:

2.40Å R-factor: 0.242 R-free: 0.295

Authors:

Y.Alguel,C.Meng,W.Teran,T.Krell,J.L.Ramos,M.-T.Gallegos,X.Zhang

Key ref:

Y.Alguel et al. (2007). Crystal structures of multidrug binding protein TtgR in complex with antibiotics and plant antimicrobials. J Mol Biol, 369, 829-840. PubMed id: 17466326 DOI: 10.1016/j.jmb.2007.03.062

Date:

28-Mar-07 Release date: 08-May-07

Protein chains

Q9AIU0  (TTGR_PSEPT) -  HTH-type transcriptional regulator TtgR from Pseudomonas putida (strain DOT-T1E)

Seq: 210 a.a.

Struc: 206 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.jmb.2007.03.062

J Mol Biol 369:829-840 (2007)

PubMed id: 17466326

Crystal structures of multidrug binding protein TtgR in complex with antibiotics and plant antimicrobials.

Y.Alguel, C.Meng, W.Terán, T.Krell, J.L.Ramos, M.T.Gallegos, X.Zhang.

ABSTRACT

Antibiotic resistance is a widely spread phenomenon. One major mechanism that underlies antibiotic resistance in bacteria is the active extrusion of toxic compounds through the membrane-bound efflux pumps that are often regulated at the transcriptional level. TtgR represses the transcription of TtgABC, a key efflux pump in Pseudomonas putida, which is highly resistant to antibiotics, solvents and toxic plant secondary products. Previously we showed that TtgR is the only reported repressor that binds to different classes of natural antimicrobial compounds, which are also extruded by the efflux pump. We report here five high-resolution crystal structures of TtgR from the solvent-tolerant strain DOT-T1E, including TtgR in complex with common antibiotics and plant secondary metabolites. We provide structural basis for the unique ligand binding properties of TtgR. We identify two distinct and overlapping ligand binding sites; the first one is broader and consists of mainly hydrophobic residues, whereas the second one is deeper and contains more polar residues including Arg176, a unique residue present in the DOT-T1E strain but not in other Pseudomonas strains. Phloretin, a plant antimicrobial, can bind to both binding sites with distinct binding affinities and stoichiometries. Results on ligand binding properties of native and mutant TtgR proteins using isothermal titration calorimetry confirm the binding affinities and stoichiometries, and suggest a potential positive cooperativity between the two binding sites. The importance of Arg176 in phloretin binding was further confirmed by the reduced ability of phloretin in releasing the mutant TtgR from bound DNA compared to the native protein. The results presented here highlight the importance and versatility of regulatory systems in bacterial antibiotic resistance and open up new avenues for novel antimicrobial development.

Selected figure(s)

Figure 2.

Figure 3.
Figure 3. Detailed effector binding and interactions. (a) Chemical structures of the effector molecules characterized in this study. (b) Tetracycline binding. (c) Chloramphenicol binding. (d) Naringenin binding. (e) Quercetin binding. (f) High affinity phloretin binding. (g) Low affinity phloretin binding. Effector molecules are displayed as sticks. Residues contributing to the binding sites are labelled and colour-coded according to atomic properties. O, red; N, blue; C, white for protein or yellow for ligand; S, orange; Cl, green. Interactions between ligands and TtgR residues as well as water molecules (red spheres) are represented by broken lines. Ligand binding sites were analysed using PyMol with a 3.6 Å cut off for hydrogen bonds.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2007, 369, 829-840) copyright 2007.

Figures were selected by the author.