title: An ABC transporter with two periplasmic binding proteins involved in iron acquisition in Pseudomonas aeruginosa.
abstract: Pyoverdine I is the main siderophore secreted byPseudomonas aeruginosa PAO1 to obtain access to iron. After extracellular iron chelation, pyoverdine-Fe uptake into the bacteria involves a specific outer-membrane transporter, FpvA. Iron is then released in the periplasm by a mechanism involving no siderophore modification but probably iron reduction. The proteins involved in this dissociation step are currently unknown. The pyoverdine locus contains the fpvCDEF operon, which contains four genes. These genes encode an ABC transporter of unknown function with the distinguishing characteristic of encompassing two periplasmic binding proteins, FpvC and FpvF, associated with the ATPase, FpvE, and the permease, FpvD. Deletion of these four genes partially inhibited cytoplasmic uptake of (55)Fe in the presence of pyoverdine and markedly slowed down the in vivo kinetics of iron release from the siderophore. This transporter is therefore involved in iron acquisition by pyoverdine in P. aeruginosa. Sequence alignments clearly showed that FpvC and FpvF belong to two different subgroups of periplasmic binding proteins. FpvC appears to be a metal-binding protein, whereas FpvF has homology with ferrisiderophore binding proteins. In vivo cross-linking assays and incubation of purified FpvC and FpvF proteins showed formation of complexes between both proteins. These complexes were able to bind in vitro PVDI-Fe, PVDI-Ga, or apo PVDI. This is the first example of an ABC transporter involved in iron acquisition via siderophores, with two periplasmic binding proteins interacting with the ferrisiderophore. The possible roles of FpvCDEF in iron uptake by the PVDI pathway are discussed.
authors.affiliation: UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant, F-67412 Illkirch, Strasbourg, France.
authors.forename: Karl
authors.initials: K
authors.lastname: Brillet
authors.forename: Frank
authors.initials: F
authors.lastname: Ruffenach
authors.forename: Hendrik
authors.initials: H
authors.lastname: Adams
authors.forename: Laure
authors.initials: L
authors.lastname: Journet
authors.forename: Véronique
authors.initials: V
authors.lastname: Gasser
authors.forename: Francoise
authors.initials: F
authors.lastname: Hoegy
authors.forename: Laurent
authors.initials: L
authors.lastname: Guillon
authors.forename: Mélissa
authors.initials: M
authors.lastname: Hannauer
authors.forename: Adeline
authors.initials: A
authors.lastname: Page
authors.forename: Isabelle J
authors.initials: IJ
authors.lastname: Schalk
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005798:Genes, Bacterial; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D019897:Periplasm / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D007501:Iron