title: Active transport of iron and siderophore antibiotics.
abstract: Bacteria solubilize iron (Fe(3+)) with secreted siderophores, which are then taken up as Fe(3+)-siderophore complexes. Some bacteria also use iron in heme, hemoglobin, hemopexin, transferrin and lactoferrin of eukaryotic hosts. Crystal structures of two outer membrane transport proteins, FhuA and FepA, and biochemical data reveal strong long-range conformational changes of the proteins upon binding of Fe(3+)-siderophore complexes and in response to energy transfer from the cytoplasmic membrane into the outer membrane via the TonB-ExbB-ExbD protein complex. The crystal structure of the periplasmic binding protein FhuD strongly deviates from the uniform overall structure of binding proteins hitherto determined. Sideromycins, antibiotics that contain Fe(3+)-siderophore complexes as carriers, are highly effective, as they enter cells via Fe(3+)-siderophore transport systems. In this review, recently published data is discussed to demonstrate the state of understanding of iron transport across the outer membrane and the cytoplasmic membrane.
authors.affiliation: Mikrobiologie/Membranphysiologie, Universität Tübingen, Auf der Morgenstelle 28, D-72076, Tübingen, Germany. volkmar.braun@mikrobio.uni-tuebingen.de
authors.forename: Volkmar
authors.initials: V
authors.lastname: Braun
authors.forename: Michael
authors.initials: M
authors.lastname: Braun
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism*; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides; D033902:Periplasmic Binding Proteins; D011487:Protein Conformation; D011956:Receptors, Cell Surface; D011991:Receptors, Virus / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D005290:Ferric Compounds; D005296:Ferrous Compounds; C050900:FhuA protein, E coli; D026901:Membrane Transport Proteins; D010455:Peptides; D033902:Periplasmic Binding Proteins; D011956:Receptors, Cell Surface; D011991:Receptors, Virus; C029489:enterobactin receptor; C069969:fhuD protein, E coli; C016738:sideromycins; D007501:Iron