A complex of ExbB, ExbD, and TonB couples cytoplasmic membrane (CM) proton motive force (pmf) to the active transport of large, scarce, or important nutrients across the outer membrane (OM). TonB interacts with OM transporters to enable ligand transport. Several mechanical models and a shuttle model explain how TonB might work. In the mechanical models, TonB remains attached to the CM during en...

The siderophore transport activities of the two outer membrane proteins FhuA and FecA of Escherichia coli require the proton motive force of the cytoplasmic membrane. The energy of the proton motive force is postulated to be transduced to the transport proteins by a protein complex that consists of the TonB, ExbB, and ExbD proteins. In the present study, TonB fragments lacking the cytoplasmic m...

The ferric hydroxamate uptake receptor FhuA from Escherichia coli transports siderophores across the outer membrane (OM). TonB-ExbB-ExbD transduces energy from the cytoplasmic membrane to the OM by contacts between TonB and OM receptors that contain the Ton box, a consensus sequence near the N terminus. Although the Ton box is a region of known contact between OM receptors and TonB, our biophys...

TonB protein appears to couple the electrochemical potential of the cytoplasmic membrane to active transport across the essentially unenergized outer membrane of gram-negative bacteria. ExbB protein has been identified as an auxiliary protein in this process. In this paper we show that ExbD protein, encoded by an adjacent gene in the exb cluster at 65', was also required for TonB-dependent ener...

BACKGROUND The aim of this study was to produce a recombinant version of the highly antigenic Helicobacter pylori TonB (iron-dependent siderophore transporter protein HP1341) in transgenic plants as a candidate oral vaccine antigen. MATERIALS AND METHODS Using Agrobacterium-mediated gene transfer, we introduced three different constructs of the tonB gene into the genome of the model plant Ara...

Haemophilus influenzae can utilize iron-loaded human transferrin as an iron source for growth in vitro. H. influenzae tonB mutants, containing a chloramphenicol acetyltransferase gene within their tonB genes, could bind iron-charged human transferrin to their cell surfaces, but they were unable to utilize this serum glycoprotein as the sole source of iron for growth in vitro. In contrast, these...

The cytoplasmic membrane protein TonB spans the periplasm of the Gram-negative bacterial cell envelope, contacts cognate outer membrane receptors, and facilitates siderophore transport. The outer membrane receptor FhuA from Escherichia coli mediates TonB-dependent import of ferrichrome. We report the 3.3 angstrom resolution crystal structure of the TonB carboxyl-terminal domain in complex with ...

By cloning into Escherichia coli and construction of isogenic mutants of Haemophilus ducreyi, we showed that the hemoglobin receptor (HgbA) is TonB dependent. An E. coli hemA tonB mutant expressing H. ducreyi hgbA grew on low levels of hemoglobin as a source of heme only when an intact H. ducreyi Ton system plasmid was present. In contrast, growth on heme by the E. coli hemA tonB mutant express...

Transport of vitamin B(12) across the outer membrane of Escherichia coli, like that of iron-siderophore complexes, is an active transport process requiring a specific outer membrane transporter BtuB, the proton motive force, and the trans-periplasmic energy coupling protein TonB. Interaction between TonB and two of the TonB-dependent siderophore transporters has been detected previously by form...

Gram-negative bacteria acquire iron with TonB-dependent uptake systems. The TonB-ExbBD inner membrane complex is hypothesized to transfer energy to outer membrane (OM) iron transporters. Fluorescence microscopic characterization of green fluorescent protein (GFP)-TonB hybrid proteins revealed an unexpected, restricted localization of TonB in the cell envelope. Fluorescence polarization measurem...