scholarly journals An Excretory Function for the Escherichia coli Outer Membrane Pore TolC: Upregulation of marA and soxS Transcription and Rob Activity Due to Metabolites Accumulated in tolC Mutants

2009 ◽  
Vol 191 (16) ◽  
pp. 5283-5292 ◽  
Author(s):  
Judah L. Rosner ◽  
Robert G. Martin
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Bile Salts ◽  
Efflux Pumps ◽  
Membrane Channel ◽  
Protein Activity ◽  
Membrane Pore ◽  
Excretory Function ◽  
Outer Membrane Channel ◽  
Transcriptional Fusions

ABSTRACT Efflux pumps function to rid bacteria of xenobiotics, including antibiotics, bile salts, and organic solvents. TolC, which forms an outer membrane channel, is an essential component of several efflux pumps in Escherichia coli. We asked whether TolC has a role during growth in the absence of xenobiotics. Because tolC transcription is activated by three paralogous activators, MarA, SoxS, and Rob, we examined the regulation of these activators in tolC mutants. Using transcriptional fusions, we detected significant upregulation of marRAB and soxS transcription and Rob protein activity in tolC mutants. Three mechanisms could be distinguished: (i) activation of marRAB transcription was independent of marRAB, soxR, and rob functions; (ii) activation of soxS transcription required SoxR, a sensor of oxidants; and (iii) Rob protein was activated posttranscriptionally. This mechanism is similar to the mechanisms of upregulation of marRAB, soxS, and Rob by treatment with certain phenolics, superoxides, and bile salts, respectively. The transcription of other marA/soxS/rob regulon promoters, including tolC itself, was also elevated in tolC mutants. We propose that TolC is involved in the efflux of certain cellular metabolites, not only xenobiotics. As these metabolites accumulate during growth, they trigger the upregulation of MarA, SoxS, and Rob, which in turn upregulate tolC and help rid the bacteria of these metabolites, thereby restoring homeostasis.

TolC of Escherichia coli Functions as an Outer Membrane Channel

1993 ◽  
Vol 278 (2-3) ◽  
pp. 187-196 ◽  
Author(s):  
Roland Benz ◽  
Elke Maier ◽  
Ivaylo Gentschev
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Membrane Channel ◽  
Outer Membrane Channel

scholarly journals Function and Expression of an N-Acetylneuraminic Acid-Inducible Outer Membrane Channel in Escherichia coli

2005 ◽  
Vol 187 (6) ◽  
pp. 1959-1965 ◽  
Author(s):  
Guy Condemine ◽  
Catherine Berrier ◽  
Jacqueline Plumbridge ◽  
Alexandre Ghazi
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Structural Genes ◽  
Membrane Channel ◽  
Positive Potential ◽  
E Coli ◽  
Acetylneuraminic Acid ◽  
Catabolite Activator Protein ◽  
Intergenic Regions ◽  
Outer Membrane Channel

ABSTRACT The Escherichia coli yjhA (renamed nanC) gene encodes a protein of the KdgM family of outer membrane-specific channels. It is transcribed divergently from fimB, a gene involved in the site-specific inversion of the region controlling transcription of the fimbrial structural genes but is separated from it by one of the largest intergenic regions in E. coli. We show that nanC expression is induced by N-acetylneuraminic acid and modulated by N-acetylglucosamine. This regulation occurs via the NanR and NagC regulators, which also control fimB expression. nanC expression is also activated by the regulators cyclic AMP-catabolite activator protein, OmpR, and CpxR. When the NanC protein was reconstituted into liposomes, it formed channels with a conductance of 450 pS at positive potential and 300 to 400 pS at negative potential in 800 mM KCl. The channels had a weak anionic selectivity. In an ompR background, where the general porins OmpF and OmpC are absent, NanC is required for growth of E. coli on N-acetylneuraminic acid as the sole carbon source. All these results suggest that NanC is an N-acetylneuraminic acid outer membrane channel protein.

scholarly journals Tripartite efflux pumps: energy is required for dissociation, but not assembly or opening of the outer membrane channel of the pump

2013 ◽  
Vol 88 (3) ◽  
pp. 590-602 ◽  
Author(s):  
Thamarai K. Janganan ◽  
Vassiliy N. Bavro ◽  
Li Zhang ◽  
Maria Inês Borges‐Walmsley ◽  
Adrian R. Walmsley
Keyword(s):  
Outer Membrane ◽  
Efflux Pumps ◽  
Membrane Channel ◽  
Outer Membrane Channel

scholarly journals Single-channel measurements of an N-acetylneuraminic acid-inducible outer membrane channel in Escherichia coli

2012 ◽  
Vol 41 (3) ◽  
pp. 259-271 ◽  
Author(s):  
Janhavi Giri ◽  
John M. Tang ◽  
Christophe Wirth ◽  
Caroline M. Peneff ◽  
Bob Eisenberg
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Single Channel ◽  
Channel Measurements ◽  
Membrane Channel ◽  
Acetylneuraminic Acid ◽  
Outer Membrane Channel

Molecular Basis of Enrofloxacin Translocation through OmpF, an Outer Membrane Channel of Escherichia coli - When Binding Does Not Imply Translocation

2010 ◽  
Vol 114 (15) ◽  
pp. 5170-5179 ◽  
Author(s):  
Kozhinjampara R. Mahendran ◽  
Eric Hajjar ◽  
Tivadar Mach ◽  
Marcos Lovelle ◽  
Amit Kumar ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Molecular Basis ◽  
Membrane Channel ◽  
Outer Membrane Channel

scholarly journals Roles of TolC-Dependent Multidrug Transporters of Escherichia coli in Resistance to β-Lactams

2003 ◽  
Vol 47 (9) ◽  
pp. 3030-3033 ◽  
Author(s):  
Kunihiko Nishino ◽  
Junko Yamada ◽  
Hidetada Hirakawa ◽  
Takahiro Hirata ◽  
Akihito Yamaguchi
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Cell Division ◽  
Outer Membrane ◽  
Drug Transporters ◽  
Membrane Channel ◽  
E Coli ◽  
Multidrug Transporters ◽  
Lactam Antibiotic ◽  
Outer Membrane Channel

ABSTRACT AcrAB exports some β-lactam antibiotics in the periplasm out of cells via an outer-membrane channel, TolC. It has been reported that eight drug transporters in Escherichia coli cooperate with TolC. In this study, the roles of the drug exporters of E. coli in β-lactam resistance were examined. We found that five of five resistance-nodulation-cell division-type drug exporters confer β-lactam antibiotic resistance, while no other drug exporters confer any β-lactam resistance even when they cooperate with TolC.

scholarly journals TolC Is Involved in Enterobactin Efflux across the Outer Membrane of Escherichia coli

2005 ◽  
Vol 187 (19) ◽  
pp. 6701-6707 ◽  
Author(s):  
Corinna Bleuel ◽  
Cornelia Große ◽  
Nadine Taudte ◽  
Judith Scherer ◽  
Dirk Wesenberg ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
High Performance ◽  
Pcr Analysis ◽  
Iron Starvation ◽  
Membrane Channel ◽  
E Coli ◽  
Iron Deprivation ◽  
Outer Membrane Channel ◽  
Major Facilitator

ABSTRACT Escherichia coli excretes the catecholate siderophore enterobactin in response to iron deprivation. While the mechanisms underlying enterobactin biosynthesis and ferric enterobactin uptake and utilization are widely understood, nearly nothing is known about how enterobactin is exported from the cell. Mutant and high-performance liquid chromatography analyses demonstrated that the outer membrane channel tunnel protein TolC but none of the respective seven resistance nodulation cell division (RND) proteins CusA, AcrB, AcrD, AcrF, MdtF (YhiV), or the twin RND MdtBC (YegNO) was essential for enterobactin export across the outer membrane. Mutant E. coli strains with additional deletion of tolC or the major facilitator entS were growth deficient in iron-depleted medium. Strains with deletion of tolC or entS, but not with deletion of genes encoding RND transporters, excreted very little enterobactin into the growth medium. Enterobactin excretion in E. coli is thus probably a two-step process involving the major facilitator EntS and the outer membrane channel tunnel protein TolC. Quantitative reverse transcription-PCR analysis of gene-specific transcripts showed no significant changes in tolC expression upon iron depletion. However, iron starvation led to increased expression of the RND gene mdtF and a decrease in acrD.

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