Extracellular Iron Reductases: Identification of a New Class of Enzymes by Siderophore-Producing Microorganisms
- 1 April 1999
- journal article
- Published by Elsevier BV in Archives of Biochemistry and Biophysics
- Vol. 364 (1), 75-82
- https://doi.org/10.1006/abbi.1999.1109
Abstract
This study identifies extracellular iron reductases in culture supernatant fluids of the siderophore-producing microorganisms Escherichia coli and Pseudomonas aeruginosa. These enzymes were constitutively produced and reduced and released iron from a variety of ferric chelators. Dialyzable cofactors, necessary for the transfer of electrons in the enzymatic reduction of iron, were identified. The reductases were sensitive to treatment with proteinase K and guanidine-HCl, were not associated with siderophore activity, and were apparently released from the cell as extracellular enzymes. The acquisition of 59Fe2+ by cell suspensions of E. coli and P. aeruginosa was saturable, suggesting that the ferrous iron generated by these reductases can be bound and transported. Salmonella typhimurium mutants feoB, tonB, entB, and entBfeoB, deficient in numerous known iron uptake pathways, were found to exhibit substantial extracellular iron-reducing activities over that of the parent. A hypothesis is proposed in which the extracellular iron reductases excreted by siderophore-producing microorganisms may be responsible for the mobilization of iron during conditions of iron repletion when siderophores are repressed and may also function in concert with siderophores during periods of iron starvation.Keywords
This publication has 36 references indexed in Scilit:
- A Comparison of Bathophenanthrolinedisulfonic Acid and Ferrozine as Chelators of Iron(II) in Reduction ReactionsAnalytical Biochemistry, 1993
- Role of iron in regulation of virulence genesClinical Microbiology Reviews, 1993
- Regulation of the expression of bacterial iron transport genes: possible role of an antisense RNA as a repressorGene, 1993
- Genetics and molecular biology of siderophore-mediated iron transport in bacteriaMicrobiological Reviews, 1989
- Ferric uptake regulation protein acts as a repressor, employing iron(II) as a cofactor to bind the operator of an iron transport operon in Escherichia coliBiochemistry, 1987
- Operator sequences of the aerobactin operon of plasmid ColV-K30 binding the ferric uptake regulation (fur) repressorJournal of Bacteriology, 1987
- Promoter mapping and transcriptional regulation of the iron assimilation system of plasmid ColV-K30 in Escherichia coli K-12Journal of Bacteriology, 1985
- Regulation of ferric iron transport in Escherichia coli K12: Isolation of a constitutive mutantMolecular Genetics and Genomics, 1981
- Iron mobilization from ferritin by chelating agentsJournal of Inorganic Biochemistry, 1980
- Ferric ion sequestering agents. 2. Kinetics and mechanism of iron removal from transferrin by enterobactin and synthetic tricatecholsJournal of the American Chemical Society, 1979