title: Identification and characterization of the exbB, exbD and tonB genes of Pseudomonas putida WCS358: their involvement in ferric-pseudobactin transport.
abstract: Catechol-cephalosporins are siderophore-like antibiotics which are taken up by cells of Pseudomonas putida WCS358 via the ferric-siderophore transport pathway. Mutants of strain WCS358 were isolated that are resistant to high concentrations of these antibiotics. These mutants failed to grow under iron-limiting conditions, and could not utilize different ferric-siderophores. The mutants fall in three complementation groups. The nucleotide sequence determination identified three contiguous open reading frames, which were homologous to the exbB, exbD and tonB genes of Escherichia coli respectively. The deduced amino acid sequence of P. putida ExbB showed 58.6% homology with its E. coli homologue, but, unlike the E. coli protein, it has a N-terminal extension of 91 amino acids. The ExbD proteins are 64.8% homologous, whereas the TonB proteins only show 27.7% homology. The P. putida exbB gene could complement an E. coli exbB mutation, but the TonB proteins were not interchangeable between the species. It is concluded that P. putida WCS358 contains an energy-coupling system between the membranes, for active transport across the outer membrane, which is comprised of a TonB-like energy-transducing protein and two accessory proteins. This system is similar to, but not completely compatible with, the E. coli system.
authors.affiliation: Department of Molecular Cell Biology, University of Utrecht, The Netherlands.
authors.forename: W
authors.initials: W
authors.lastname: Bitter
authors.forename: J
authors.initials: J
authors.lastname: Tommassen
authors.forename: P J
authors.initials: PJ
authors.lastname: Weisbeek
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001693:Biological Transport, Active; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D007501:Iron / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism*; D016366:Open Reading Frames; D016958:Pseudomonas putida / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D017262:Siderophores / Q000378:metabolism; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C052874:ExbB protein, E coli; D008565:Membrane Proteins; D009842:Oligopeptides; D017262:Siderophores; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli; C060790:exbD protein, E coli; C033038:pseudobactin; D007501:Iron