title: The PvdRT-OpmQ efflux pump controls the metal selectivity of the iron uptake pathway mediated by the siderophore pyoverdine in Pseudomonas aeruginosa.
abstract: Pyoverdine (PVD) is the major siderophore produced by Pseudomonas aeruginosa for iron acquisition. PvdRT-OpmQ is an ATP-dependent efflux pump involved in the secretion of newly synthesized pyoverdine (PVD) and of PVD that has transported and released its iron into the bacterium from the periplasm into the extracellular medium. This iron uptake pathway also involves an outer membrane transporter, FpvA, for PVD-Fe uptake from the extracellular medium into the periplasm. In binding assays, FpvA bound PVD in complex with many different metals, with affinities from 2.9 nM for PVD-Fe to 13 µM for PVD-Al. Uptake assays with various FpvA and PvdRT-OpmQ mutants, monitored by inductively coupled plasma-atomic emission spectrometry (ICP-AES) for metal detection, and by fluorescence for PVD detection, showed that both metals and PVD accumulated in P. aeruginosa, due to the uptake of these compounds via the FpvA/PVD pathway. Higher levels of accumulation were observed in the absence of PvdRT-OpmQ expression. Thus, FpvA has a broad metal specificity for both the binding and uptake of PVD-metal complexes, and the PvdRT-OpmQ efflux pump exports unwanted metals complexed with PVD from the bacterium. This study provides the first evidence of efflux pump involvement in the export of unwanted siderophore-metal complexes and insight into the molecular mechanisms involved controlling the metal selectivity of siderophore-mediated iron uptake pathways.
authors.affiliation: Université de Strasbourg-CNRS, Blvd Sébastien Brant, Illkirch, Strasbourg, France.
authors.forename: Mélissa
authors.initials: M
authors.lastname: Hannauer
authors.forename: Armelle
authors.initials: A
authors.lastname: Braud
authors.forename: Françoise
authors.initials: F
authors.lastname: Hoegy
authors.forename: Pascale
authors.initials: P
authors.lastname: Ronot
authors.forename: Anne
authors.initials: A
authors.lastname: Boos
authors.forename: Isabelle J
authors.initials: IJ
authors.lastname: Schalk
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001692:Biological Transport; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008670:Metals / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism*; D019897:Periplasm / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D017262:Siderophores / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001425:Bacterial Outer Membrane Proteins; C082326:FpvA protein, Pseudomonas aeruginosa; D026901:Membrane Transport Proteins; D008670:Metals; D009842:Oligopeptides; D017262:Siderophores; C042453:pyoverdin; D007501:Iron