ExbB and ExbD proteins are part of the TonB-dependent energy transduction system and are encoded by the exb operon in Escherichia coli. TonB, the energy transducer, appears to go through a cycle during energy transduction, with the absence of both ExbB and ExbD creating blocks at two points: (i) in the inability of TonB to respond to the cytoplasmic membrane proton motive force and (ii) in the ...

The universal colicin-indicator strain Escherichia coli phi, unlike E. coli strain K-12, is sensitive to pesticin, a bacteriocin produced by wild-type Yersinia pestis. Eleven distinct phenotypes of E. coli phi mutants were obtained by selection for insensitivity to pesticin, group B colicins, the group A colicin S4, or coliphage T5. Representative isolates from eight of these classes closely re...

In gram-negative bacteria, high-affinity iron uptake requires the TonB/ExbB/ExbD envelope complex to release iron chelates from their specific outer membrane receptors into the periplasm. Based on sequence similarities, the Bordetella pertussis tonB exbB exbD locus was identified on a cloned DNA fragment. The tight organization of the three genes suggests that they are cotranscribed. A putative...

The TonB system of gram-negative bacteria energizes the active transport of diverse nutrients through high-affinity TonB-gated outer membrane transporters using energy derived from the cytoplasmic membrane proton motive force. Cytoplasmic membrane proteins ExbB and ExbD harness the proton gradient to energize TonB, which directly contacts and transmits this energy to ligand-loaded transporters....

The TonB protein located in the cell wall of Gram-negative bacteria mediates the proton motive force from the cytoplasmic membrane to specific outer membrane transporters. A C-terminal fragment of TonB from Escherichia coli consisting of amino-acid residues 147-239 (TonB-92) has been purified and crystallized. Crystals grew in space group P2(1) to dimensions of about 1.0 x 0.12 x 0.12 mm. A nat...

In Yersinia pestis, the siderophore-dependent yersiniabactin (Ybt) iron transport system and heme transport system (Hmu) have putative TonB-dependent outer membrane receptors. Here we demonstrate that hemin uptake and iron utilization from Ybt are TonB dependent. However, the Yfe iron and manganese transport system does not require TonB.

TonB from Escherichia coli and its homologues are critical for the uptake of siderophores through the outer membrane of Gram-negative bacteria using chemiosmotic energy. When different models for the mechanism of TonB mediated energy transfer from the inner to the outer membrane are discussed, one of the key questions is whether TonB spans the periplasm. In this article, we use long range dista...

In Gram-negative bacteria, the import of essential micronutrients across the outer membrane requires a transporter, an electrochemical gradient of protons across the inner membrane, and an inner membrane protein complex (ExbB, ExbD, TonB) that couples the proton-motive force to the outer membrane transporter. The inner membrane protein TonB binds directly to a conserved region, called the Ton-b...

In Gram-negative bacteria like Escherichia coli the ExbB-ExbD-TonB protein complex is anchored to the cytoplasmic membrane and is involved in energization of outer membrane transport. Outer membrane proteins catalyze energy-coupled transport of scarce nutrients. Energy is derived from the protonmotive force of the cytoplasmic membrane which is transferred through ExbB-ExbD-TonB to the outer mem...

The ferric hydroxymate uptake (FhuA) receptor from Escherichia coli facilitates transport of siderophores ferricrocin and ferrichrome and siderophore-antibiotic conjugates such as albomycin and rifamycin CGP 4832. FhuA is also the receptor for phages T5, T1, Phi80, UC-1, for colicin M and for the antimicrobial peptide microcin MccJ21. Energy for transport is provided by the cytoplasmic membrane...