Ferric Uptake Regulator (FUR) protein: properties and implications in cyanobacteria

2015 ◽  
Vol 66 (1) ◽  
pp. 61-75 ◽  
Author(s):  
Manish Singh Kaushik ◽  
Prashant Singh ◽  
Balkrishna Tiwari ◽  
Arun Kumar Mishra
Keyword(s):  
Ferric Uptake Regulator ◽  
Protein Properties ◽  
Fur Protein

scholarly journals Ferric uptake regulator (Fur) reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis in Escherichia coli

2020 ◽  
Vol 295 (46) ◽  
pp. 15454-15463 ◽  
Author(s):  
Chelsey R. Fontenot ◽  
Homyra Tasnim ◽  
Kathryn A. Valdes ◽  
Codrina V. Popescu ◽  
Huangen Ding
Keyword(s):  
Escherichia Coli ◽  
Iron Content ◽  
Iron Homeostasis ◽  
Ferric Uptake Regulator ◽  
Intracellular Iron ◽  
Free Iron ◽  
E Coli ◽  
Genes Encoding ◽  
Fur Protein ◽  
Mutant Cells

The ferric uptake regulator (Fur) is a global transcription factor that regulates intracellular iron homeostasis in bacteria. The current hypothesis states that when the intracellular “free” iron concentration is elevated, Fur binds ferrous iron, and the iron-bound Fur represses the genes encoding for iron uptake systems and stimulates the genes encoding for iron storage proteins. However, the “iron-bound” Fur has never been isolated from any bacteria. Here we report that the Escherichia coli Fur has a bright red color when expressed in E. coli mutant cells containing an elevated intracellular free iron content because of deletion of the iron–sulfur cluster assembly proteins IscA and SufA. The acid-labile iron and sulfide content analyses in conjunction with the EPR and Mössbauer spectroscopy measurements and the site-directed mutagenesis studies show that the red Fur protein binds a [2Fe-2S] cluster via conserved cysteine residues. The occupancy of the [2Fe-2S] cluster in Fur protein is ∼31% in the E. coli iscA/sufA mutant cells and is decreased to ∼4% in WT E. coli cells. Depletion of the intracellular free iron content using the membrane-permeable iron chelator 2,2´-dipyridyl effectively removes the [2Fe-2S] cluster from Fur in E. coli cells, suggesting that Fur senses the intracellular free iron content via reversible binding of a [2Fe-2S] cluster. The binding of the [2Fe-2S] cluster in Fur appears to be highly conserved, because the Fur homolog from Hemophilus influenzae expressed in E. coli cells also reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis.

scholarly journals A Dominant-Negative fur Mutation in Bradyrhizobium japonicum

2004 ◽  
Vol 186 (5) ◽  
pp. 1409-1414 ◽  
Author(s):  
Heather P. Benson ◽  
Kristin LeVier ◽  
Mary Lou Guerinot
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Iron Uptake ◽  
Outer Membrane Proteins ◽  
Dominant Negative ◽  
Ferric Uptake Regulator ◽  
Null Mutant ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Fur Protein

ABSTRACT In many bacteria, the ferric uptake regulator (Fur) protein plays a central role in the regulation of iron uptake genes. Because iron figures prominently in the agriculturally important symbiosis between soybean and its nitrogen-fixing endosymbiont Bradyrhizobium japonicum, we wanted to assess the role of Fur in the interaction. We identified a fur mutant by selecting for manganese resistance. Manganese interacts with the Fur protein and represses iron uptake genes. In the presence of high levels of manganese, bacteria with a wild-type copy of the fur gene repress iron uptake systems and starve for iron, whereas fur mutants fail to repress iron uptake systems and survive. The B. japonicum fur mutant, as expected, fails to repress iron-regulated outer membrane proteins in the presence of iron. Unexpectedly, a wild-type copy of the fur gene cannot complement the fur mutant. Expression of the fur mutant allele in wild-type cells leads to a fur phenotype. Unlike a B. japonicum fur-null mutant, the strain carrying the dominant-negative fur mutation is unable to form functional, nitrogen-fixing nodules on soybean, mung bean, or cowpea, suggesting a role for a Fur-regulated protein or proteins in the symbiosis.

scholarly journals Influence of the ferric uptake regulator (Fur) protein on pathogenicity in Pectobacterium carotovorum subsp. brasiliense

PLoS ONE ◽  
2017 ◽  
Vol 12 (5) ◽  
pp. e0177647 ◽  
Author(s):  
Collins Kipngetich Tanui ◽  
Divine Yutefar Shyntum ◽  
Stefan Louis Priem ◽  
Jacques Theron ◽  
Lucy Novungayo Moleleki
Keyword(s):  
Pectobacterium Carotovorum ◽  
Ferric Uptake Regulator ◽  
Fur Protein ◽  
Carotovorum Subsp

scholarly journals Regulation of Iron Uptake by Fine-Tuning the Iron Responsiveness of the Iron Sensor Fur

2019 ◽  
Vol 85 (9) ◽  
Author(s):  
Jeongjoon Choi ◽  
Sangryeol Ryu
Keyword(s):  
Iron Uptake ◽  
Metal Ion ◽  
Iron Homeostasis ◽  
Control Mechanism ◽  
Fine Tuning ◽  
Ferric Uptake Regulator ◽  
Biological Processes ◽  
Iron Availability ◽  
Fur Protein ◽  
Iron Concentrations

ABSTRACTIron is one of most abundant environmental metal ions but is highly limited in organisms. It is an important metal ion as it facilitates various biological processes, including catalysis of metabolic enzymes and DNA biogenesis. In bacteria, the ferric uptake regulator (Fur) protein controls iron uptake by regulating genes coding for iron transporters in response to iron concentration. This iron response is ascribed to Fur’s intrinsic affinity for iron because its binding to iron dictates its regulatory function. However, we now report that the pathogenSalmonellaachieves a proper response of Fur to changes in environmental iron concentrations via EIIANtr(a nitrogen metabolic phosphotransferase system component). We establish that EIIANtrincreases expression of iron transporter-coding genes under low-iron conditions (i.e., nanomolar ranges) in a Fur-dependent manner, which promotesSalmonellagrowth under such conditions. EIIANtrdirectly hampers Fur binding to DNA, thereby inducing expression of those genes. This regulation allowsSalmonellato express Fur-regulated genes under low-iron conditions. Our findings reveal a potentially widespread control mechanism of bacterial iron uptake systems operating in response to iron availability.IMPORTANCEIron is a fundamental metal ion for living organisms as it facilitates various biological processes. The ferric uptake regulator (Fur) protein controls iron homeostasis in various bacterial species. It is believed that Fur’s iron-dependent regulatory action is sufficient for it to function as an iron sensor. However, we now establish that the bacterial pathogenSalmonellaenables Fur to properly reflect changes in surrounding iron availability by fine-tuning its responsiveness to iron. This process requires a protein that hampers Fur DNA binding at low iron concentrations. In this way,Salmonellabroadens the range of iron concentrations that Fur responds to. Our findings reveal a potentially widespread control mechanism of bacterial iron homeostasis.

scholarly journals Regulation of fur Expression by RpoS and Fur in Vibrio vulnificus

2003 ◽  
Vol 185 (19) ◽  
pp. 5891-5896 ◽  
Author(s):  
Hyun-Jung Lee ◽  
Kyung-Je Park ◽  
Ah Young Lee ◽  
Sung Goo Park ◽  
Byoung Chul Park ◽  
...  
Keyword(s):  
Gene Product ◽  
Mutant Strain ◽  
Sigma Factor ◽  
Proteomic Analysis ◽  
Vibrio Vulnificus ◽  
Protein A ◽  
Ferric Uptake Regulator ◽  
Wild Type ◽  
Fur Protein

ABSTRACT In a proteomic analysis of rpoS-deficient Vibrio vulnificus versus the wild type, one of the down-regulated proteins in the rpoS mutant strain was identified as a Fur protein, a ferric uptake regulator. The expression of a fur::luxAB fusion was significantly influenced by sigma factor S, the rpoS gene product, and positively regulated by Fur under iron-limited conditions.

scholarly journals Bacillus subtilis Fur represses one of two paralogous haem-degrading monooxygenases

Microbiology ◽  
2011 ◽  
Vol 157 (11) ◽  
pp. 3221-3231 ◽  
Author(s):  
Ahmed Gaballa ◽  
John D. Helmann
Keyword(s):  
Bacillus Subtilis ◽  
Active Site ◽  
Iron Uptake ◽  
Iron Limitation ◽  
Ferric Uptake Regulator ◽  
Spectroscopic Analyses ◽  
Family Protein ◽  
Fur Protein ◽  
Mechanisms Of Adaptation

Identification of genes regulated by the ferric uptake regulator (Fur) protein has provided insights into the diverse mechanisms of adaptation to iron limitation. In the soil bacterium Bacillus subtilis, Fur senses iron sufficiency and represses genes that enable iron uptake, including biosynthetic and transport genes for the siderophore bacillibactin and uptake systems for siderophores produced by other organisms. We here demonstrate that Fur regulates hmoA (formerly yetG), which encodes a haem monooxygenase. HmoA is the first characterized member of a divergent group of putative monooxygenases that cluster separately from the well-characterized IsdG family. B. subtilis also encodes an IsdG family protein designated HmoB (formerly YhgC). Unlike hmoA, hmoB is constitutively expressed and not under Fur control. HmoA and HmoB both bind haemin in vitro with approximately 1 : 1 stoichiometry and degrade haemin in the presence of an electron donor. Mutational and spectroscopic analyses indicate that HmoA and HmoB have distinct active site architectures and interact differently with haem. We further show that B. subtilis can use haem as an iron source, but that this ability is independent of HmoA and HmoB.

scholarly journals Biochemical analysis of the recombinant Fur (ferric uptake regulator) protein from Anabaena PCC 7119: factors affecting its oligomerization state

2002 ◽  
Vol 366 (1) ◽  
pp. 315-322 ◽  
Author(s):  
José A. HERNÁNDEZ ◽  
M. Teresa BES ◽  
María F. FILLAT ◽  
José L. NEIRA ◽  
M. Luisa PELEATO
Keyword(s):  
Polyclonal Antibodies ◽  
Ferric Uptake Regulator ◽  
Ionization Time ◽  
Factors Affecting ◽  
Nitrobenzoic Acid ◽  
Regulator Protein ◽  
Iron Deficient ◽  
Significant Difference ◽  
Cyanobacterium Anabaena ◽  
Fur Protein

Fur (ferric uptake regulator) protein is a DNA-binding protein which regulates iron-responsive genes. Recombinant Fur from the nitrogen-fixing cyanobacterium Anabaena PCC 7119 has been purified and characterized, and polyclonal antibodies obtained. The experimental data show that Fur from Anabaena dimerizes in solution with the involvement of disulphide bridges. Cross-linking experiments and MALDI-TOF (matrix-assisted laser desorption/ionization time of flight) MS also show several oligomerization states of Fur, and the equilibrium of these forms depends on protein concentration and ionic strength. In intact recombinant Fur, four cysteine residues out of five were inert towards DTNB [5,5′-dithiobis-(2-nitrobenzoic acid)], and their modification required sodium borohydride. Metal analysis and electrospray ionization MS revealed that neither zinc nor other metals are present in this Fur protein. Purified recombinant Fur bound to its own promoter in gel-shift assays. Fur was shown to be a constitutive protein in Anabaena cells, with no significant difference in its expression in cells grown under iron-sufficient compared with iron-deficient conditions.

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