PDBsum entry: 1lnw

Transcription repressor

PDB id: 1lnw

Contents

Protein chains

(+ 0 more) 141 a.a. *

130 a.a. *

Waters ×214

* Residue conservation analysis

PDB id:

1lnw

Name:

Transcription repressor

Title:

Crystal structure of the mexr repressor of the mexab-oprm multidrug efflux operon of pseudomonas aeruginosa

Structure:

Multidrug resistance operon repressor. Chain: a, b, c, d, e, f, g, h. Synonym: mexr. Engineered: yes

Source:

Pseudomonas aeruginosa. Organism_taxid: 287. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PQS)

Resolution:

2.10Å R-factor: 0.242 R-free: 0.294

Authors:

D.C.Lim,K.Poole,N.C.J.Strynadka

Key ref:

D.Lim et al. (2002). Crystal structure of the MexR repressor of the mexRAB-oprM multidrug efflux operon of Pseudomonas aeruginosa. J Biol Chem, 277, 29253-29259. PubMed id: 12034710 DOI: 10.1074/jbc.M111381200

Date:

03-May-02 Release date: 11-Sep-02

Protein chains

P52003  (MEXR_PSEAE) -  Multidrug resistance operon repressor

Seq: 147 a.a.

Struc: 141 a.a.

Protein chains

P52003  (MEXR_PSEAE) -  Multidrug resistance operon repressor

Seq: 147 a.a.

Struc: 130 a.a.

 Gene Ontology (GO) functional annotation 

• Cellular component: intracellular (1 term)
• Biological process: regulation of transcription (3 terms)
• Biochemical function: DNA binding (2 terms)

DOI no: 10.1074/jbc.M111381200

J Biol Chem 277:29253-29259 (2002)

PubMed id: 12034710

Crystal structure of the MexR repressor of the mexRAB-oprM multidrug efflux operon of Pseudomonas aeruginosa.

D.Lim, K.Poole, N.C.Strynadka.

ABSTRACT

MexR is a member of the MarR family of bacterial transcriptional regulators and is the repressor for the MexAB-OprM operon, which encodes a tripartite multidrug efflux system in Pseudomonas aeruginosa. Mutations in MexR result in increased resistance to multiple antibiotics due to overexpression of this efflux system. We have determined the crystal structure of MexR to 2.1-A resolution in the absence of effector. The four copies of the MexR dimer in the asymmetric unit are observed in multiple conformations. Analysis of these conformational states in the context of a model of the MexR-DNA complex proposed in this study suggests that an effector-induced conformational change may inhibit DNA binding by reducing the spacing of the DNA binding domains. The inhibited conformation is exhibited by one of the four MexR dimers, which contains an ordered C-terminal tail from a neighboring monomer inserted between its DNA binding domains and which we propose may resemble the MexR-effector complex. Our results indicate that MexR may differ from the other described member of this family, MarR, in the nature of its effector, mode of DNA binding, and mechanism of regulation.

Selected figure(s)

Figure 1.
Fig. 1. Overall structure of the MexR dimer. a, MexR dimer in ribbon representation. The secondary structure elements are labeled and colored individually in the monomer on the right. The winged helix domain (colored blue in the monomer on the left) consists of 2 (H1)- 1 (S1)- 3 (H2)- 4 (H3, recognition helix)- 2 (S2)-W1 (wing)- 3 (S3), where the terminology used by Gajiwala and Burley (24) is given in brackets. The N and C termini are labeled N and C, respectively. b, MexR dimer shown in similar orientation as in a and with a GRASP (43) molecular surface representation of one subunit highlighting the hydrophobic dimerization interface. Low, medium, and high hydrophobic potentials are colored gray, yellow, and green, respectively. The second subunit is shown in ribbon respresentation (magenta).

Figure 3.
Fig. 3. Proposed mechanism of regulation of MexR. a, molecular modeling of MexR-DNA complex. The MexR dimer CD (ribbon representation) depicts the "open" or DNA-bound conformation. The DNA molecule is shown in stick representation, with the inverted repeats colored green and highlighted by thick rendering. Residues on MexR which correspond to the MarR residues observed to be in contact with salicylate (23) are shown in stick rendering. b, insertion of the C-terminal tail (residues 140-147 shown with magenta carbons) from chain C in between the DNA binding domains results in a "closed" conformation depicted by dimer AB (ribbon representation), in which the reduced spacing between the DNA binding domains is incompatible with the spacing of the inverted repeats (green with thick rendering) of the operator. SigmaA-weighted 2F[o] F[c] electron density (29) is contoured at 1 to 2.1 Å around the C-terminal tail. The electron density object was created in O (44). c, close-up view of the interactions between the C-terminal tail of monomer C (magenta) with side chains on monomer A. d, close-up view of the interactions between the C-terminal tail of monomer C (magenta) with the side chains on monomer B. Water molecules are shown as red spheres in c and d. e, electrophoretic mobility shift assays of DNA binding by SeMet MexR with and without treatment with Hinc II restriction endonuclease. All samples contained 247 ng of a 28-bp DNA oligonucleotide with the sequence 5'ATTTTAGTT GACCTTATCAACCTTGTTT (the HincII site is in bold with the cleavage site indicated by ) corresponding to the MexR binding site II identified by previous footprinting studies (26). The DNA in lanes 3 and 4 were digested with HincII for 1 h and 40 min at 37 °C. Prior to loading onto the gel, 12.8 µg of SeMet-substituted MexR protein were added to samples in lanes 2 and 4.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2002, 277, 29253-29259) copyright 2002.

Figures were selected by an automated process.