title: Specific TonB-ExbB-ExbD energy transduction systems required for ferric enterobactin acquisition in Campylobacter.
abstract: Ferric enterobactin (FeEnt) acquisition plays a critical role in the pathophysiology of Campylobacter, the leading bacterial cause of human gastroenteritis in industrialized countries. In Campylobacter, the surface-exposed receptor, CfrA or CfrB, functions as a 'gatekeeper' for initial binding of FeEnt. Subsequent transport across the outer membrane is energized by TonB-ExbB-ExbD energy transduction systems. Although there are up to three TonB-ExbB-ExbD systems in Campylobacter, the cognate components of TonB-ExbB-ExbD for FeEnt acquisition are still largely unknown. In this study, we addressed this issue using complementary molecular approaches: comparative genomic analysis, random transposon mutagenesis and site-directed mutagenesis in two representative C. jejuni strains, NCTC 11168 and 81-176. We demonstrated that CfrB could interact with either TonB2 or TonB3 for efficient Ent-mediated iron acquisition. However, TonB3 is a dominant player in the CfrA-dependent pathway. The ExbB2 and ExbD2 components were essential for both CfrA- and CfrB-dependent FeEnt acquisition. Sequences analysis identified potential TonB boxes in CfrA and CfrB, and the corresponding binding sites in TonB. In conclusion, these findings identify specific TonB-ExbB-ExbD energy transduction components required for FeEnt acquisition, and provide insights into the complex molecular interactions of FeEnt acquisition systems in Campylobacter.
authors.affiliation: Department of Animal Science, The University of Tennessee, Knoxville, TN, USA.
authors.forename: Ximin
authors.initials: X
authors.lastname: Zeng
authors.forename: Fuzhou
authors.initials: F
authors.lastname: Xu
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002167:Campylobacter / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D004758:Enterobactin / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D011956:Receptors, Cell Surface / Q000378:metabolism; D016415:Sequence Alignment; D017262:Siderophores / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D017262:Siderophores; C029489:enterobactin receptor; C057616:tonB protein, Bacteria; D004758:Enterobactin; D007501:Iron
keywords: iron uptake; molecular mechanism; siderophore
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