title: The csbX gene of Azotobacter vinelandii encodes an MFS efflux pump required for catecholate siderophore export.
abstract: The csbX gene of Azotobacter vinelandii was regulated in an iron-repressible manner from a divergent promoter upstream of the catecholate siderophore biosynthesis (csb) operon and was predicted to encode an efflux pump of the major facilitator superfamily. Other proteins that were most similar to CsbX were encoded by genes found in the catecholate siderophore biosynthesis operons of Aeromonas hydrophila and Stigmatella aurantiaca. Inactivation of csbX resulted in 57-100% decrease in the amount of catecholates released when compared to the wild-type in iron-limited medium. CsbX was most important for the export of the high affinity chelator protochelin with the majority of the catecholates released by csbX mutants being the protochelin intermediates azotochelin and aminochelin.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9. bill.page@ualberta.ca
authors.forename: William J
authors.initials: WJ
authors.lastname: Page
authors.forename: Elena
authors.initials: E
authors.lastname: Kwon
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Cornish
authors.forename: Anne E
authors.initials: AE
authors.lastname: Tindale
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D016948:Azotobacter vinelandii / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D001692:Biological Transport; D002396:Catechols / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D023061:Gene Order; D005798:Genes, Bacterial; D007501:Iron / Q000494:pharmacology; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D017262:Siderophores / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002396:Catechols; D004269:DNA, Bacterial; D008565:Membrane Proteins; D017262:Siderophores; D007501:Iron