Roles of the EnvZ/OmpR Two-Component System and Porins in Iron Acquisition in .

secretes high-affinity Fe chelators to solubilize and transport chelated Fe via specific outer membrane receptors. In microaerobic and anaerobic growth environments, where the reduced Fe form is predominant, ferrous transport systems fulfill the bacterial need for iron. Expression of genes coding for iron metabolism is controlled by Fur, which when bound to Fe acts as a repressor.

Reversal of the Drug Binding Pocket Defects of the AcrB Multidrug Efflux Pump Protein of Escherichia coli.

Unlabelled: The AcrB protein of Escherichia coli, together with TolC and AcrA, forms a contiguous envelope conduit for the capture and extrusion of diverse antibiotics and cellular metabolites. In this study, we sought to expand our knowledge of AcrB by conducting genetic and functional analyses. We began with an AcrB mutant bearing an F610A substitution in the drug binding pocket and obtained second-site substitutions that overcame the antibiotic hypersusceptibility phenotype conferred by the F610A mutation.