This paper provides the biochemical evidence for physical interactions between the outer membrane component, TolC, and the membrane fusion protein component, AcrA, of the major antibiotic efflux pump of Escherichia coli. Cross-linking between TolC and AcrA was independent of the presence of any externally added substrate of the efflux pump or of the pump protein, AcrB. The biochemical demonstra...

When Legionella pneumophila grows on agar plates, it secretes a surfactant that promotes flagellum- and pilus-independent "sliding" motility. We isolated three mutants that were defective for surfactant. The first two had mutations in genes predicted to encode cytoplasmic enzymes involved in lipid metabolism. These genes mapped to two adjacent operons that we designated bbcABCDEF and bbcGHIJK. ...

Pneumonia associated with Iegionnaires's disease is initiated in humans after inhalation of contaminated aerosols. In the environment, Legionella pneumophila is thought to survive and multiply as an intracellular parasite within free-living amoeba. In the genome of L. pneumophila Lens, we identified a unique gene, tolC, encoding a protein that is highly homologous to the outer membrane protein ...

We found that Escherichia coli tolC mutants showed increased sensitivity to 5-aminolevulinic acid (ALA), a precursor of porphyrins. The tolC mutant cells grown in the presence of ALA showed a reddish brown color under visible light and a strong red fluorescence under near-UV irradiation. Fluorescence spectrometry and high-performance liquid chromatography analysis showed that the tolC mutant ce...

Mutation in the tolC locus greatly reduces normal synthesis of OmpF, a major porin protein of Escherichia coli K-12. Experiments that use ompF-ompC chimeric genes demonstrate that a tolC mutation exerts its effect at either the promoter or the amino-terminal end of the ompF gene. Direct analysis of ompF mRNA from tolC+ and tolC strains showed that the amount of ompF transcript in the latter was...

OBJECTIVES The Gram-negative human pathogen Klebsiella oxytoca is often resistant to several antibiotics such as fluoroquinolones, erythromycin, tetracycline, chloramphenicol and others. The aim of this study was to look at the mechanisms leading to this resistance and particularly the role of TolC and efflux mechanisms in determining resistance. METHODS Ciprofloxacin accumulation was measure...

Many transporters of Gram-negative bacteria involved in the extracellular secretion of proteins and the efflux of toxic molecules operate by forming intermembrane complexes. These complexes are proposed to span both inner and outer membranes and create a bridge across the periplasm. In this study, we analyzed interactions between the inner and outer membrane components of the tri-partite multid...

OBJECTIVES TolC is a major outer membrane channel and it plays an important role in the excretion of a wide range of molecules, including antibiotics. A recent study has shown that Salmonella enterica serovar Typhimurium has nine functional drug efflux pumps; however, the TolC dependency of these efflux pumps remains to be studied in detail. The aim of this study was to investigate the TolC dep...

TolC is a multifunctional outer-membrane protein (OMP) of Escherichia coli that folds into a unique alpha/beta-barrel structure. Previous studies have shown that unlike the biogenesis of beta-barrel OMPs, such as porins, TolC assembles independently from known periplasmic folding factors. Yet, the assembly of TolC, like that of beta-barrel OMPs, is dependent on BamA and BamD, two essential comp...

A Tn5 insertion in tolC eliminated microcin J25 production. The mutation had little effect on the expression of the microcin structural gene and presumably acted by blocking microcin secretion. The tolC mutants carrying multiple copies of the microcin genes were less immune to the microcin. TolC is thus likely a component of a microcin export complex containing the McjD immunity protein, an ABC...