title: Alr0397 is an outer membrane transporter for the siderophore schizokinen in Anabaena sp. strain PCC 7120.
abstract: Iron uptake in proteobacteria by TonB-dependent outer membrane transporters represents a well-explored subject. In contrast, the same process has been scarcely investigated in cyanobacteria. The heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 is known to secrete the siderophore schizokinen, but its transport system has remained unidentified. Inspection of the genome of strain PCC 7120 shows that only one gene encoding a putative TonB-dependent iron transporter, namely alr0397, is positioned close to genes encoding enzymes involved in the biosynthesis of a hydroxamate siderophore. The expression of alr0397, which encodes an outer membrane protein, was elevated under iron-limited conditions. Inactivation of this gene caused a moderate phenotype of iron starvation in the mutant cells. The characterization of the mutant strain showed that Alr0397 is a TonB-dependent schizokinen transporter (SchT) of the outer membrane and that alr0397 expression and schizokinen production are regulated by the iron homeostasis of the cell.
authors.affiliation: JWGU Frankfurt am Main, CEF-Macromolecular Complexes, Center of Membrane Proteomics, Department of Biosciences, Max-von-Laue Str. 9, 60439 Frankfurt, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Nicolaisen
authors.forename: Suncana
authors.initials: S
authors.lastname: Moslavac
authors.forename: Anastazia
authors.initials: A
authors.lastname: Samborski
authors.forename: Marianne
authors.initials: M
authors.lastname: Valdebenito
authors.forename: Klaus
authors.initials: K
authors.lastname: Hantke
authors.forename: Iris
authors.initials: I
authors.lastname: Maldener
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Muro-Pastor
authors.forename: Enrique
authors.initials: E
authors.lastname: Flores
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001692:Biological Transport; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006877:Hydroxamic Acids / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D008957:Models, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013054:Spectrophotometry, Atomic
chemical_list: D001425:Bacterial Outer Membrane Proteins; D006877:Hydroxamic Acids; C000766:schizokinen; D007501:Iron