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PDBsum entry 2uxh
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Transcription
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PDB id
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2uxh
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References listed in PDB file
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Key reference
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Title
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Crystal structures of multidrug binding protein ttgr in complex with antibiotics and plant antimicrobials.
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Authors
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Y.Alguel,
C.Meng,
W.Terán,
T.Krell,
J.L.Ramos,
M.T.Gallegos,
X.Zhang.
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Ref.
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J Mol Biol, 2007,
369,
829-840.
[DOI no: ]
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PubMed id
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Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
percentage match of
95%.
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Abstract
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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.
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Figure 2.
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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.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2007,
369,
829-840)
copyright 2007.
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