title: Actinobacillus pleuropneumoniae iron transport: a set of exbBD genes is transcriptionally linked to the tbpB gene and required for utilization of transferrin-bound iron.
abstract: Upon iron restriction, Actinobacillus pleuropneumoniae has been shown to express the transferrin-binding proteins TbpB and TbpA, both of which have been implied to be important virulence factors. In order to identify additional iron-regulated proteins, we cloned and analyzed the region upstream of the transferrin-binding protein genes in an A. pleuropneumoniae serotype 7 strain. We located immediately upstream of the tbpB gene two open reading frames which were 43% homologous to the neisserial ExbBD protein genes. By raising specific antibodies, we showed that ExbB is expressed under iron-limiting growth conditions only, and RT-PCR analysis revealed that the exbBD genes and the tbpB gene are transcribed on a single polycistronic mRNA. By constructing an isogenic and nonpolar exbBD mutant, we showed that the exbBD genes are required by A. pleuropneumoniae for utilization of transferrin-bound iron. Using PCR and Western blotting, we showed that the genetic organization found in A. pleuropneumoniae serotype 7 is similar in all 12 A. pleuropneumoniae serotype reference strains.
authors.affiliation: Institut für Mikrobiologie und Tierseuchen, Tierärztliche Hochschule Hannover, 30173 Hannover, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Tonpitak
authors.forename: S
authors.initials: S
authors.lastname: Thiede
authors.forename: W
authors.initials: W
authors.lastname: Oswald
authors.forename: N
authors.initials: N
authors.lastname: Baltes
authors.forename: G F
authors.initials: GF
authors.lastname: Gerlach
mesh_terms: D016977:Actinobacillus pleuropneumoniae / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D014158:Transcription, Genetic; D014168:Transferrin / Q000378:metabolism*; D033863:Transferrin-Binding Proteins
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D033862:Iron-Binding Proteins; D014168:Transferrin; D033863:Transferrin-Binding Proteins; C060790:exbD protein, E coli; D007501:Iron