AcrAB-TolC is the major multidrug efflux system in Enterobacteriaceae recognizing structurally unrelated molecules including antibiotics, dyes, and detergents. Additionally, in Escherichia coli it mediates resistance to bile salts. In the plant pathogen Erwinia amylovora AcrAB-TolC is required for virulence and phytoalexin resistance. Exchange analysis of AcrAB-TolC was conducted by complementi...

OBJECTIVES Starting from the observation that Escherichia coli tolC mutations severely reduced the high-level resistance to tetracycline afforded by Tn10- and plasmid-encoded Tet(A) pumps, we studied the mechanism of this susceptibility. METHODS The MIC of tetracycline for MC4100 tolC::Tn10 and several tolC mutants carrying the Tn10 in other sites on the chromosome (thr::Tn10) was determined....

A study examining the influence of TolC on AcrA, AcrR, and MarR1 mutants indicates that functional TolC is required for the operation of the AcrAB efflux system and for the expression of the Mar phenotype. That the effect of TolC on the AcrAB pump is not regulatory in nature is shown by studies measuring the influence of a tolC::Tn10 insertion mutation on the expression of an acrA::lacZ reporte...

The TolC protein of Escherichia coli, through its interaction with AcrA and AcrB, is thought to form a continuous protein channel that expels inhibitors from the cell. Consequently, tolC null mutations display a hypersensitive phenotype. Here we report the isolation and characterization of tolC missense mutations that direct the synthesis of mutant TolC proteins partially disabled in their effl...

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...

About 10% of the nalidixic acid-resistant (Nal(r)) mutants in a transposition-induced library exhibited a growth factor requirement as the result of cysH, icdA, metE, or purB mutation. Resistance in all of these mutants required a functional AcrAB-TolC efflux pump, but the EmrAB-TolC pump played no obvious role. Transcription of acrAB was increased in each type of Nal(r) mutant. In the icdA and...

OBJECTIVES Multidrug efflux pumps mediate resistance to antibiotics and other toxic compounds. We studied the role of AcrAB-TolC, the main efflux pump in Escherichia coli, in regulating gene expression. METHODS Deletion mutants, an acrABp-lacZ fusion and reverse transcription-real-time quantitative PCR experiments were used to study the role of AcrAB-TolC and metabolism in regulating gene exp...