In gram-negative bacteria, the cytoplasmic membrane proton-motive force energizes the active transport of TonB-dependent ligands through outer membrane TonB-gated transporters. In Escherichia coli, cytoplasmic membrane proteins ExbB and ExbD couple the proton-motive force to conformational changes in TonB, which are hypothesized to form the basis of energy transduction through direct contact wi...

TonB, in complex with ExbB and ExbD, is required for the energy-dependent transport of ferric siderophores across the outer membrane of Escherichia coli, the killing of cells by group B colicins, and infection by phages T1 and phi80. To gain insights into the protein complex, TonB dimerization was studied by constructing hybrid proteins from complete TonB (containing amino acids 1 to 239) [TonB...

The TonB box, a conserved pentapeptide sequence found in TonB-dependent colicins and receptors, is thought to interact physically with the TonB protein to facilitate TonB-dependent processes. Strains of Escherichia coli were treated in vivo with the synthetic TonB box pentapeptide Glu-Thr-Val-Ile-Val. The pentapeptide inhibited several TonB-dependent processes, including cell growth in low-iron...

TonB protein of Escherichia coli couples the electrochemical potential of the cytoplasmic membrane (CM) to active transport of iron-siderophores and vitamin B(12) across the outer membrane (OM). TonB interacts with OM receptors and transduces conformationally stored energy. Energy for transport is provided by the proton motive force through ExbB and ExbD, which form a ternary complex with TonB ...

TonB-dependent transporters are β-barrel outer membrane proteins that depend on interactions with the inner membrane protein TonB to drive import of scarce nutrients. Upon becoming ligand-loaded, TonB-dependent transporters bind TonB through a β-strand exchange. FhuA is the TonB-dependent transporter that transports hydroxamate iron siderophores, such as ferrichrome and ferricrocin, into the pe...

The transport of Fe(III)-siderophore complexes and vitamin B12 across the outer membrane of Escherichia coli is an active transport process requiring a cognate outer membrane receptor, cytoplasmic membrane-derived proton motive force, and an energy-transducing protein anchored in the cytoplasmic membrane, TonB. This process requires direct physical contact between the outer membrane receptor an...

We created hybrid proteins to study the functions of TonB. We first fused the portion of Escherichia coli tonB that encodes the C-terminal 69 amino acids (amino acids 170 to 239) of TonB downstream from E. coli malE (MalE-TonB69C). Production of MalE-TonB69C in tonB(+) bacteria inhibited siderophore transport. After overexpression and purification of the fusion protein on an amylose column, we ...

Both induction of transcription of the ferric citrate transport genes and transport of ferric citrate by the Escherichia coli outer membrane receptor FecA require energy derived from the proton motive force (PMF) of the inner membrane. The energy is transduced to FecA by the inner membrane complex, TonB, ExbB, and ExbD. Region 160 of TonB and the conserved TonB box of other TonB-dependent recep...

To investigate the contribution of the TonB protein to high-affinity iron acquisition in Pseudomonas aeruginosa, we constructed tonB-inactivated mutants from strain PAO1 and its derivative deficient in producing the siderophores pyoverdin and pyochelin. The tonB mutants could not grow in a free-iron-restricted medium prepared by apotransferrin addition, even though the medium was supplemented w...

The TonB system couples cytoplasmic membrane proton motive force to TonB-gated outer membrane transporters for active transport of nutrients into the periplasm. In Escherichia coli, cytoplasmic membrane proteins ExbB and ExbD promote conformational changes in TonB, which transmits this energy to the transporters. The only known energy-dependent interaction occurs between the periplasmic domains...