Logo of jbacterPermissionsJournals.ASM.orgJournalJB ArticleJournal InfoAuthorsReviewers
J Bacteriol. 1997 Nov; 179(22): 7103–7110.
PMCID: PMC179653

Unusual structure of the tonB-exb DNA region of Xanthomonas campestris pv. campestris: tonB, exbB, and exbD1 are essential for ferric iron uptake, but exbD2 is not.


The nucleotide sequence of a 3.6-kb HindIII-SmaI DNA fragment of Xanthomonas campestris pv. campestris revealed four open reading frames which, based on sequence homologies, were designated tonB, exbB, exbD1, and exbD2. Analysis of translational fusions to alkaline phosphatase and beta-galactosidase confirmed that the TonB, ExbB, ExbD1, and ExbD2 proteins are anchored in the cytoplasmic membrane. The TonB protein of X. campestris pv. campestris lacks the conserved (Glu-Pro)n and (Lys-Pro)m repeats but harbors a 13-fold repeat of proline residues. By mutational analysis, the tonB, exbB, and exbD1 genes were shown to be essential for ferric iron import in X. campestris pv. campestris. In contrast, the exbD2 gene is not involved in the uptake of ferric iron.

Full Text

The Full Text of this article is available as a PDF (694K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Aguilar OM, Kapp D, Pühler A. Characterization of a Rhizobium meliloti fixation gene (fixF) located near the common nodulation region. J Bacteriol. 1985 Oct;164(1):245–254. [PMC free article] [PubMed]
  • Ahmer BM, Thomas MG, Larsen RA, 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 Aug;177(16):4742–4747. [PMC free article] [PubMed]
  • Arnold W, Pühler A. A family of high-copy-number plasmid vectors with single end-label sites for rapid nucleotide sequencing. Gene. 1988 Oct 15;70(1):171–179. [PubMed]
  • Bachmann BJ. Linkage map of Escherichia coli K-12, edition 8. Microbiol Rev. 1990 Jun;54(2):130–197. [PMC free article] [PubMed]
  • Backman K, Ptashne M, Gilbert W. Construction of plasmids carrying the cI gene of bacteriophage lambda. Proc Natl Acad Sci U S A. 1976 Nov;73(11):4174–4178. [PMC free article] [PubMed]
  • Becker A, Niehaus K, Pühler A. Low-molecular-weight succinoglycan is predominantly produced by Rhizobium meliloti strains carrying a mutated ExoP protein characterized by a periplasmic N-terminal domain and a missing C-terminal domain. Mol Microbiol. 1995 Apr;16(2):191–203. [PubMed]
  • Becker A, Rüberg S, Küster H, Roxlau AA, Keller M, Ivashina T, Cheng HP, Walker GC, Pühler A. The 32-kilobase exp gene cluster of Rhizobium meliloti directing the biosynthesis of galactoglucan: genetic organization and properties of the encoded gene products. J Bacteriol. 1997 Feb;179(4):1375–1384. [PMC free article] [PubMed]
  • Becker A, Schmidt M, Jäger W, Pühler A. New gentamicin-resistance and lacZ promoter-probe cassettes suitable for insertion mutagenesis and generation of transcriptional fusions. Gene. 1995 Aug 30;162(1):37–39. [PubMed]
  • Bitter W, Tommassen J, Weisbeek PJ. Identification and characterization of the exbB, exbD and tonB genes of Pseudomonas putida WCS358: their involvement in ferric-pseudobactin transport. Mol Microbiol. 1993 Jan;7(1):117–130. [PubMed]
  • Bradbeer C. The proton motive force drives the outer membrane transport of cobalamin in Escherichia coli. J Bacteriol. 1993 May;175(10):3146–3150. [PMC free article] [PubMed]
  • Braun V. The structurally related exbB and tolQ genes are interchangeable in conferring tonB-dependent colicin, bacteriophage, and albomycin sensitivity. J Bacteriol. 1989 Nov;171(11):6387–6390. [PMC free article] [PubMed]
  • 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 Jul;16(4):295–307. [PubMed]
  • 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 Apr;8(2):261–268. [PubMed]
  • Deng WP, Nickoloff JA. Site-directed mutagenesis of virtually any plasmid by eliminating a unique site. Anal Biochem. 1992 Jan;200(1):81–88. [PubMed]
  • 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 Sep;171(9):5117–5126. [PMC free article] [PubMed]
  • Expert D, Enard C, Masclaux C. The role of iron in plant host-pathogen interactions. Trends Microbiol. 1996 Jun;4(6):232–237. [PubMed]
  • Fellay R, Krisch HM, Prentki P, Frey J. Omegon-Km: a transposable element designed for in vivo insertional mutagenesis and cloning of genes in gram-negative bacteria. Gene. 1989;76(2):215–226. [PubMed]
  • Gaisser S, Braun V. The tonB gene of Serratia marcescens: sequence, activity and partial complementation of Escherichia coli tonB mutants. Mol Microbiol. 1991 Nov;5(11):2777–2787. [PubMed]
  • Hancock RW, Braun V. Nature of the energy requirement for the irreversible adsorption of bacteriophages T1 and phi80 to Escherichia coli. J Bacteriol. 1976 Feb;125(2):409–415. [PMC free article] [PubMed]
  • Härle C, Kim I, Angerer A, Braun V. Signal transfer through three compartments: transcription initiation of the Escherichia coli ferric citrate transport system from the cell surface. EMBO J. 1995 Apr 3;14(7):1430–1438. [PMC free article] [PubMed]
  • Heller KJ, Kadner RJ, Günther K. Suppression of the btuB451 mutation by mutations in the tonB gene suggests a direct interaction between TonB and TonB-dependent receptor proteins in the outer membrane of Escherichia coli. Gene. 1988 Apr 15;64(1):147–153. [PubMed]
  • Hötte B, Rath-Arnold I, Pühler A, Simon R. Cloning and analysis of a 35.3-kilobase DNA region involved in exopolysaccharide production by Xanthomonas campestris pv. campestris. J Bacteriol. 1990 May;172(5):2804–2807. [PMC free article] [PubMed]
  • Jarosik GP, Hansen EJ. Cloning and sequencing of the Haemophilus influenzae exbB and exbD genes. Gene. 1995 Jan 11;152(1):89–92. [PubMed]
  • Kammler M, Schön C, Hantke K. Characterization of the ferrous iron uptake system of Escherichia coli. J Bacteriol. 1993 Oct;175(19):6212–6219. [PMC free article] [PubMed]
  • Kamoun S, Kado CI. A plant-inducible gene of Xanthomonas campestris pv. campestris encodes an exocellular component required for growth in the host and hypersensitivity on nonhosts. J Bacteriol. 1990 Sep;172(9):5165–5172. [PMC free article] [PubMed]
  • Kampfenkel K, Braun V. Membrane topology of the Escherichia coli ExbD protein. J Bacteriol. 1992 Aug;174(16):5485–5487. [PMC free article] [PubMed]
  • Kampfenkel K, Braun V. Topology of the ExbB protein in the cytoplasmic membrane of Escherichia coli. J Biol Chem. 1993 Mar 15;268(8):6050–6057. [PubMed]
  • Katzen F, Becker A, Zorreguieta A, Pühler A, Ielpi L. Promoter analysis of the Xanthomonas campestris pv. campestris gum operon directing biosynthesis of the xanthan polysaccharide. J Bacteriol. 1996 Jul;178(14):4313–4318. [PMC free article] [PubMed]
  • Koebnik R, Bäumler AJ, Heesemann J, Braun V, Hantke K. The TonB protein of Yersinia enterocolitica and its interactions with TonB-box proteins. Mol Gen Genet. 1993 Feb;237(1-2):152–160. [PubMed]
  • Koster M, van Klompenburg W, Bitter W, Leong J, Weisbeek P. Role for the outer membrane ferric siderophore receptor PupB in signal transduction across the bacterial cell envelope. EMBO J. 1994 Jun 15;13(12):2805–2813. [PMC free article] [PubMed]
  • Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein. J Mol Biol. 1982 May 5;157(1):105–132. [PubMed]
  • Larsen RA, Wood GE, Postle K. The conserved proline-rich motif is not essential for energy transduction by Escherichia coli TonB protein. Mol Microbiol. 1993 Dec;10(5):943–953. [PubMed]
  • Lipman DJ, Pearson WR. Rapid and sensitive protein similarity searches. Science. 1985 Mar 22;227(4693):1435–1441. [PubMed]
  • McClure WR. Mechanism and control of transcription initiation in prokaryotes. Annu Rev Biochem. 1985;54:171–204. [PubMed]
  • Meade HM, Long SR, Ruvkun GB, Brown SE, Ausubel FM. Physical and genetic characterization of symbiotic and auxotrophic mutants of Rhizobium meliloti induced by transposon Tn5 mutagenesis. J Bacteriol. 1982 Jan;149(1):114–122. [PMC free article] [PubMed]
  • Mende J, Braun V. Import-defective colicin B derivatives mutated in the TonB box. Mol Microbiol. 1990 Sep;4(9):1523–1533. [PubMed]
  • Neilands JB. Microbial iron compounds. Annu Rev Biochem. 1981;50:715–731. [PubMed]
  • Platt T. Transcription termination and the regulation of gene expression. Annu Rev Biochem. 1986;55:339–372. [PubMed]
  • Postle K. TonB and the gram-negative dilemma. Mol Microbiol. 1990 Dec;4(12):2019–2025. [PubMed]
  • Priefer UB. Genes involved in lipopolysaccharide production and symbiosis are clustered on the chromosome of Rhizobium leguminosarum biovar viciae VF39. J Bacteriol. 1989 Nov;171(11):6161–6168. [PMC free article] [PubMed]
  • Sanger F, Nicklen S, Coulson AR. DNA sequencing with chain-terminating inhibitors. Proc Natl Acad Sci U S A. 1977 Dec;74(12):5463–5467. [PMC free article] [PubMed]
  • Schwyn B, Neilands JB. Universal chemical assay for the detection and determination of siderophores. Anal Biochem. 1987 Jan;160(1):47–56. [PubMed]
  • Simon R, Hötte B, Klauke B, Kosier B. Isolation and characterization of insertion sequence elements from gram-negative bacteria by using new broad-host-range, positive selection vectors. J Bacteriol. 1991 Feb;173(4):1502–1508. [PMC free article] [PubMed]
  • Skare JT, Ahmer BM, Seachord CL, Darveau RP, 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 Aug 5;268(22):16302–16308. [PubMed]
  • Skare JT, Postle K. Evidence for a TonB-dependent energy transduction complex in Escherichia coli. Mol Microbiol. 1991 Dec;5(12):2883–2890. [PubMed]
  • Staden R. The current status and portability of our sequence handling software. Nucleic Acids Res. 1986 Jan 10;14(1):217–231. [PMC free article] [PubMed]
  • Steinmann D, Wiggerich HG, Klauke B, Schramm U, Pühler A, Priefer UB. Saturation mutagenesis in Escherichia coli of a cloned Xanthomonas campestris DNA fragment with the lux transposon Tn4431 using the delivery plasmid pDS1, thermosensitive in replication. Appl Microbiol Biotechnol. 1993 Nov;40(2-3):356–360. [PubMed]
  • Stojiljkovic I, Srinivasan N. Neisseria meningitidis tonB, exbB, and exbD genes: Ton-dependent utilization of protein-bound iron in Neisseriae. J Bacteriol. 1997 Feb;179(3):805–812. [PMC free article] [PubMed]
  • Stormo GD, Schneider TD, Gold LM. Characterization of translational initiation sites in E. coli. Nucleic Acids Res. 1982 May 11;10(9):2971–2996. [PMC free article] [PubMed]
  • Sun TP, Webster RE. Nucleotide sequence of a gene cluster involved in entry of E colicins and single-stranded DNA of infecting filamentous bacteriophages into Escherichia coli. J Bacteriol. 1987 Jun;169(6):2667–2674. [PMC free article] [PubMed]
  • Ubben D, Schmitt R. A transposable promoter and transposable promoter probes derived from Tn1721. Gene. 1987;53(1):127–134. [PubMed]
  • Vieira J, Messing J. New pUC-derived cloning vectors with different selectable markers and DNA replication origins. Gene. 1991 Apr;100:189–194. [PubMed]
  • Webster RE. The tol gene products and the import of macromolecules into Escherichia coli. Mol Microbiol. 1991 May;5(5):1005–1011. [PubMed]

Articles from Journal of Bacteriology are provided here courtesy of American Society for Microbiology (ASM)


Save items

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


  • Compound
    PubChem Compound links
  • Conserved Domains
    Conserved Domains
    Link to related CDD entry
  • Gene
    Gene links
  • MedGen
    Related information in MedGen
  • Nucleotide
    Published Nucleotide sequences
  • Protein
    Published protein sequences
  • PubMed
    PubMed citations for these articles
  • Substance
    PubChem Substance links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...