title: Pyochelin-mediated iron transport in Pseudomonas aeruginosa: involvement of a high-molecular-mass outer membrane protein.
abstract: An iron-regulated outer membrane protein of 75,000 daltons was strongly expressed following iron limitation of strains of Pseudomonas aeruginosa which fail to produce pyoverdine. A mutant nonderepressible for this protein (K372) was deficient in pyochelin-mediated iron transport at 150 nM FeCl3, consistent with a role for the 75-kDa protein in ferripyochelin transport. Moreover, ferripyochelin specifically protected the 75-kDa protein against trypsin digestion, supporting an interaction between ferripyochelin and the 75-kDa protein. Previous reports implicated a 14,000-dalton outer membrane protein as the receptor for ferripyochelin (P.A. Sokol and D.E. Woods, Infect. Immun. 40:665-669, 1983) and demonstrated that a mutant (FBP-28) expressing a defective 14-kDa outer membrane protein did not exhibit pyochelin-mediated iron transport (P.A. Sokol, J. Bacteriol. 169:3365-3368, 1987). Nonetheless, we were able to demonstrate (i) that FBP-28 was inducible for the 75-kDa protein under iron-limiting conditions and (ii) that concomitant with the induction of this protein in FBP-28, pyochelin-mediated iron uptake at 150 nM FeCl3 was observed. Interestingly, strain K372 did transport ferripyochelin at higher (750 nM) FeCl3 concentrations, suggesting that a second pyochelin-mediated iron transport system, perhaps involving the 14-kDa outer membrane protein identified previously, operates in P. aeruginosa.
authors.affiliation: Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, Canada.
authors.forename: D E
authors.initials: DE
authors.lastname: Heinrichs
authors.forename: L
authors.initials: L
authors.lastname: Young
authors.forename: K
authors.initials: K
authors.lastname: Poole
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis*; D001692:Biological Transport; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000378:metabolism*; D008970:Molecular Weight; D010636:Phenols / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D014357:Trypsin / Q000494:pharmacology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D007502:Iron Chelating Agents; D010636:Phenols; C025315:ferripyochelin; D007501:Iron; D014357:Trypsin