title: 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.
abstract: 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.
authors.affiliation: Lehrstuhl für Genetik, Fakultät für Biologie, Universität Bielefeld, Germany.
authors.forename: H G
authors.initials: HG
authors.lastname: Wiggerich
authors.forename: B
authors.initials: B
authors.lastname: Klauke
authors.forename: R
authors.initials: R
authors.lastname: Köplin
authors.forename: U B
authors.initials: UB
authors.lastname: Priefer
authors.forename: A
authors.initials: A
authors.lastname: Pühler
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics; D000595:Amino Acid Sequence; D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D018274:Electroporation; D029968:Escherichia coli Proteins; D015870:Gene Expression; D005973:Glutamine / Q000235:genetics; D007501:Iron / Q000378:metabolism*; D008239:Lysine / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D011392:Proline / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D017262:Siderophores / Q000378:metabolism; D014170:Transformation, Genetic; D016959:Xanthomonas campestris / Q000235:genetics* / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C052874:ExbB protein, E coli; D008565:Membrane Proteins; D017262:Siderophores; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli; D005973:Glutamine; C060790:exbD protein, E coli; D011392:Proline; D007501:Iron; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase; D008239:Lysine