Gene Symbol: exbD
Description: membrane spanning protein in TonB-ExbB-ExbD complex
Alias: ECK2998, JW2973
Species: Escherichia coli str. K-12 substr. MG1655

Top Publications

  1. Higgs P, Larsen R, Postle K. Quantification of known components of the Escherichia coli TonB energy transduction system: TonB, ExbB, ExbD and FepA. Mol Microbiol. 2002;44:271-81 pubmed
    ..TonB, the energy-transducing protein; and two cytoplasmic membrane proteins with less defined roles, ExbB and ExbD. In this study, we report the per cell numbers of TonB, ExbB, ExbD and FepA for cells grown under iron-replete and ..
  2. Braun V, Herrmann C. Point mutations in transmembrane helices 2 and 3 of ExbB and TolQ affect their activities in Escherichia coli K-12. J Bacteriol. 2004;186:4402-6 pubmed
    ..E176 and T148 are strictly conserved in ExbB and TolQ proteins, and T181 is almost strictly conserved in ExbB, TolQ, and MotA. ..
  3. Braun V. Iron uptake by Escherichia coli. Front Biosci. 2003;8:s1409-21 pubmed
    ..by the proton motive force of the cytoplasmic membrane and transmitted to the outer membrane via the TonB-ExbB-ExbD proteins...
  4. Cronan J, Silbert D, Wulff D. Mapping of the fabA locus for unsaturated fatty acid biosynthesis in Escherichia coli. J Bacteriol. 1972;112:206-11 pubmed
    ..5 of the linkage map of E. coli. The locus is cotransduced with pyrD and aroA but not with pyrC, purB, or pdxC. The clockwise order of markers in the region is pdxC, aroA, cmlB, pyrD, fabA, pyrC. ..
  5. Killmann H, Braun V. Energy-dependent receptor activities of Escherichia coli K-12: mutated TonB proteins alter FhuA receptor activities to phages T5, T1, phi 80 and to colicin M. FEMS Microbiol Lett. 1994;119:71-6 pubmed
    The activity of the FhuA receptor in the outer membrane of Escherichia coli is dependent on the TonB, ExbB and ExbD proteins which are anchored to the cytoplasmic membrane...
  6. Ollis A, Kumar A, Postle K. The ExbD periplasmic domain contains distinct functional regions for two stages in TonB energization. J Bacteriol. 2012;194:3069-77 pubmed publisher
    ..Cytoplasmic membrane proteins ExbB and ExbD harness the proton gradient to energize TonB, which directly contacts and transmits this energy to ligand-loaded ..
  7. Ollis A, Postle K. ExbD mutants define initial stages in TonB energization. J Mol Biol. 2012;415:237-47 pubmed publisher
    Cytoplasmic membrane proteins ExbB and ExbD of the Escherichia coli TonB system couple cytoplasmic membrane protonmotive force (pmf) to TonB. TonB transmits this energy to high-affinity outer membrane active transporters...
  8. Sverzhinsky A, Fabre L, Cottreau A, Biot Pelletier D, Khalil S, Bostina M, et al. Coordinated rearrangements between cytoplasmic and periplasmic domains of the membrane protein complex ExbB-ExbD of Escherichia coli. Structure. 2014;22:791-7 pubmed publisher
    Gram-negative bacteria rely on the ExbB-ExbD-TonB system for the import of essential nutrients...
  9. Ollis A, Postle K. Identification of functionally important TonB-ExbD periplasmic domain interactions in vivo. J Bacteriol. 2012;194:3078-87 pubmed publisher
    ..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 ..

More Information


  1. Ollis A, Manning M, Held K, Postle K. Cytoplasmic membrane protonmotive force energizes periplasmic interactions between ExbD and TonB. Mol Microbiol. 2009;73:466-81 pubmed publisher
    The TonB system of Escherichia coli (TonB/ExbB/ExbD) transduces the protonmotive force (pmf) of the cytoplasmic membrane to drive active transport by high-affinity outer membrane transporters...
  2. Garcia Herrero A, Peacock R, Howard S, Vogel H. The solution structure of the periplasmic domain of the TonB system ExbD protein reveals an unexpected structural homology with siderophore-binding proteins. Mol Microbiol. 2007;66:872-89 pubmed
    ..Together, the three components of the system, TonB, ExbB and ExbD, energize the transport of iron complexes through the outer membrane by utilizing the proton motive force across ..
  3. Ghosh J, Postle K. Disulphide trapping of an in vivo energy-dependent conformation of Escherichia coli TonB protein. Mol Microbiol. 2005;55:276-88 pubmed
    ..Cytoplasmic membrane proteins ExbB and ExbD appear to harvest pmf and transduce it to TonB...
  4. Higgs P, Myers P, Postle K. Interactions in the TonB-dependent energy transduction complex: ExbB and ExbD form homomultimers. J Bacteriol. 1998;180:6031-8 pubmed
    The cytoplasmic membrane proteins ExbB and ExbD support TonB-dependent active transport of iron siderophores and vitamin B12 across the essentially unenergized outer membrane of Escherichia coli...
  5. Pramanik A, Hauf W, Hoffmann J, Cernescu M, Brutschy B, Braun V. Oligomeric structure of ExbB and ExbB-ExbD isolated from Escherichia coli as revealed by LILBID mass spectrometry. Biochemistry. 2011;50:8950-6 pubmed publisher
    ..from the proton-motive force of the cytoplasmic membrane, which is coupled to the outer membrane via the ExbB-ExbD-TonB protein complex...
  6. Skare J, Ahmer B, Seachord C, Darveau R, Postle K. Energy transduction between membranes. TonB, a cytoplasmic membrane protein, can be chemically cross-linked in vivo to the outer membrane receptor FepA. J Biol Chem. 1993;268:16302-8 pubmed
    ..A tolQ nonsense mutation had no effect on the cross-linking profile observed, confirming that its participation in TonB-dependent phenomena is minor and most likely the result of evolutionary cross-talk. ..
  7. Eick Helmerich K, Braun V. Import of biopolymers into Escherichia coli: nucleotide sequences of the exbB and exbD genes are homologous to those of the tolQ and tolR genes, respectively. J Bacteriol. 1989;171:5117-26 pubmed
    ..It contained two open reading frames, designated exbB and exbD, which encoded polypeptides of 244 and 141 amino acids, respectively...
  8. Moeck G, Coulton J, Postle K. Cell envelope signaling in Escherichia coli. Ligand binding to the ferrichrome-iron receptor fhua promotes interaction with the energy-transducing protein TonB. J Biol Chem. 1997;272:28391-7 pubmed
    ..These studies demonstrate the significance of ligand binding at the external surface of the cell to mediate signal transduction across the outer membrane. ..
  9. Braun V, Herrmann C. Evolutionary relationship of uptake systems for biopolymers in Escherichia coli: cross-complementation between the TonB-ExbB-ExbD and the TolA-TolQ-TolR proteins. Mol Microbiol. 1993;8:261-8 pubmed
    ..Group B colicins, ferric siderophores and vitamin B12 are taken up via the TonB-ExbB-ExbD, group A colicins via the TolA-TolQ-TolR system...
  10. Kampfenkel K, Braun V. Membrane topology of the Escherichia coli ExbD protein. J Bacteriol. 1992;174:5485-7 pubmed
    The ExbD protein is involved in the energy-coupled transport of ferric siderophores, vitamin B12, and B-group colicins across the outer membrane of Escherichia coli...
  11. Sverzhinsky A, Chung J, Deme J, Fabre L, Levey K, Plesa M, et al. Membrane Protein Complex ExbB4-ExbD1-TonB1 from Escherichia coli Demonstrates Conformational Plasticity. J Bacteriol. 2015;197:1873-85 pubmed publisher
    ..by the proton motive force (PMF) of the cytoplasmic membrane (CM), harnessed by the CM-embedded complex of ExbB, ExbD, and TonB. Its stoichiometry, ensemble structural features, and mechanism of action are unknown...
  12. Clarke T, Tari L, Vogel H. Structural biology of bacterial iron uptake systems. Curr Top Med Chem. 2001;1:7-30 pubmed
    ..also shows that the proteins that provide energy for iron transport at the outer membrane, such as the TonB-ExbB-ExbD system, are structurally very similar across bacterial species...
  13. Ollis A, Postle K. The same periplasmic ExbD residues mediate in vivo interactions between ExbD homodimers and ExbD-TonB heterodimers. J Bacteriol. 2011;193:6852-63 pubmed publisher
    ..In Escherichia coli, cytoplasmic membrane proteins ExbB and ExbD promote conformational changes in TonB, which transmits this energy to the transporters...
  14. Braun V, Gaisser S, Herrmann C, Kampfenkel K, Killmann H, Traub I. Energy-coupled transport across the outer membrane of Escherichia coli: ExbB binds ExbD and TonB in vitro, and leucine 132 in the periplasmic region and aspartate 25 in the transmembrane region are important for ExbD activity. J Bacteriol. 1996;178:2836-45 pubmed
    ..is transferred to the outer membrane with the aid of the Ton system, consisting of the proteins TonB, ExbB, and ExbD. In this paper we describe two point mutations which inactivate ExbD...
  15. Larsen R, Letain T, Postle K. In vivo evidence of TonB shuttling between the cytoplasmic and outer membrane in Escherichia coli. Mol Microbiol. 2003;49:211-8 pubmed
    ..These findings suggest that TonB does indeed disengage from the cytoplasmic membrane during energy transduction and shuttle to the outer membrane. ..
  16. Postle K. TonB system, in vivo assays and characterization. Methods Enzymol. 2007;422:245-69 pubmed
    ..TonB, ExbB, and ExbD are required to transduce the cytoplasmic membrane energy to these transporters. For E...
  17. Hennessey E, Broome Smith J. Two related bacterial membrane proteins, ExbD and ToIR, have opposite transmembrane charge dipolarity. Mol Microbiol. 1994;11:417 pubmed
  18. Fischer E, Gunter K, Braun V. Involvement of ExbB and TonB in transport across the outer membrane of Escherichia coli: phenotypic complementation of exb mutants by overexpressed tonB and physical stabilization of TonB by ExbB. J Bacteriol. 1989;171:5127-34 pubmed
    The exb locus in Escherichia coli consists of two genes, termed exbB and exbD. Exb functions are related to TonB function in that most TonB-dependent processes are enhanced by Exb...
  19. Celia H, Noinaj N, Zakharov S, Bordignon E, Botos I, Santamaria M, et al. Structural insight into the role of the Ton complex in energy transduction. Nature. 2016;538:60-65 pubmed publisher
    ..The Ton complex consists of TonB, ExbB, and ExbD, and uses the proton motive force at the inner membrane to transduce energy to the outer membrane via TonB...
  20. Letain T, Postle K. TonB protein appears to transduce energy by shuttling between the cytoplasmic membrane and the outer membrane in Escherichia coli. Mol Microbiol. 1997;24:271-83 pubmed
    ..membrane and the outer membrane fractions, while two proteins with which it is known to interact, ExbB and ExbD, as well as the NADH oxidase activity characteristic of the cytoplasmic membrane, were localized in the cytoplasmic ..
  21. Ahmer B, Thomas M, Larsen R, Postle K. Characterization of the exbBD operon of Escherichia coli and the role of ExbB and ExbD in TonB function and stability. J Bacteriol. 1995;177:4742-7 pubmed
    ..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 energy ..
  22. Held K, Postle K. ExbB and ExbD do not function independently in TonB-dependent energy transduction. J Bacteriol. 2002;184:5170-3 pubmed
    ExbB and ExbD proteins are part of the TonB-dependent energy transduction system and are encoded by the exb operon in Escherichia coli...
  23. Braun V, Braun M. Active transport of iron and siderophore antibiotics. Curr Opin Microbiol. 2002;5:194-201 pubmed
    ..and in response to energy transfer from the cytoplasmic membrane into the outer membrane via the TonB-ExbB-ExbD protein complex...
  24. Higgs P, Letain T, Merriam K, Burke N, Park H, Kang C, et al. TonB interacts with nonreceptor proteins in the outer membrane of Escherichia coli. J Bacteriol. 2002;184:1640-8 pubmed
    ..These results suggest that there may be multiple redundant sites where TonB can interact with the outer membrane prior to transducing energy to the outer membrane receptors. ..
  25. Karlsson M, Hannavy K, Higgins C. A sequence-specific function for the N-terminal signal-like sequence of the TonB protein. Mol Microbiol. 1993;8:379-88 pubmed
  26. Braun V. Energy-coupled transport and signal transduction through the gram-negative outer membrane via TonB-ExbB-ExbD-dependent receptor proteins. FEMS Microbiol Rev. 1995;16:295-307 pubmed
    ..Energy flows from the cytoplasmic into the outer membrane via a complex consisting of the TonB, ExbB and ExbD proteins which are anchored in the cytoplasmic membrane...