scholarly journals The fission yeast ferric reductase gene frp1+ is required for ferric iron uptake and encodes a protein that is homologous to the gp91-phox subunit of the human NADPH phagocyte oxidoreductase

1993 ◽  
Vol 13 (7) ◽  
pp. 4342-4350
Author(s):  
D G Roman ◽  
A Dancis ◽  
G J Anderson ◽  
R D Klausner
Keyword(s):  
Fission Yeast ◽  
Iron Uptake ◽  
Ferric Iron ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Protein A ◽  
Mutant Gene ◽  
Predicted Amino Acid Sequence ◽  
Mrna Levels ◽  
Ferric Reductase

We have identified a cell surface ferric reductase activity in the fission yeast Schizosaccharomyces pombe. A mutant strain deficient in this activity was also deficient in ferric iron uptake, while ferrous iron uptake was not impaired. Therefore, reduction is a required step in cellular ferric iron acquisition. We have cloned frp1+, the wild-type allele of the mutant gene. frp1+ mRNA levels were repressed by iron addition to the growth medium. Fusion of 138 nucleotides of frp1+ promoter sequences to a reporter gene, the bacterial chloramphenicol acetyltransferase gene, conferred iron-dependent regulation upon the latter when introduced into S. pombe. The predicted amino acid sequence of the frp1+ gene exhibits hydrophobic regions compatible with transmembrane domains. It shows similarity to the Saccharomyces cerevisiae FRE1 gene product and the gp91-phox protein, a component of the human NADPH phagocyte oxidoreductase that is deficient in X-linked chronic granulomatous disease.

scholarly journals The fission yeast ferric reductase gene frp1+ is required for ferric iron uptake and encodes a protein that is homologous to the gp91-phox subunit of the human NADPH phagocyte oxidoreductase.

1993 ◽  
Vol 13 (7) ◽  
pp. 4342-4350 ◽  
Author(s):  
D G Roman ◽  
A Dancis ◽  
G J Anderson ◽  
R D Klausner
Keyword(s):  
Fission Yeast ◽  
Iron Uptake ◽  
Ferric Iron ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Protein A ◽  
Mutant Gene ◽  
Predicted Amino Acid Sequence ◽  
Mrna Levels ◽  
Ferric Reductase

We have identified a cell surface ferric reductase activity in the fission yeast Schizosaccharomyces pombe. A mutant strain deficient in this activity was also deficient in ferric iron uptake, while ferrous iron uptake was not impaired. Therefore, reduction is a required step in cellular ferric iron acquisition. We have cloned frp1+, the wild-type allele of the mutant gene. frp1+ mRNA levels were repressed by iron addition to the growth medium. Fusion of 138 nucleotides of frp1+ promoter sequences to a reporter gene, the bacterial chloramphenicol acetyltransferase gene, conferred iron-dependent regulation upon the latter when introduced into S. pombe. The predicted amino acid sequence of the frp1+ gene exhibits hydrophobic regions compatible with transmembrane domains. It shows similarity to the Saccharomyces cerevisiae FRE1 gene product and the gp91-phox protein, a component of the human NADPH phagocyte oxidoreductase that is deficient in X-linked chronic granulomatous disease.

High stability ferric chelates result in decreased iron uptake by the green alga Chlorella kessleri owing to decreased ferric reductase activity and chelation of ferrous iron

Botany ◽  
2009 ◽  
Vol 87 (10) ◽  
pp. 922-931 ◽  
Author(s):  
Harold G. Weger ◽  
Jackie Lam ◽  
Nikki L. Wirtz ◽  
Crystal N. Walker ◽  
Ron G. Treble
Keyword(s):  
Stability Constant ◽  
Green Alga ◽  
Iron Uptake ◽  
High Stability ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Free Form ◽  
Ferric Reductase ◽  
Chlorella Kessleri ◽  
Green Alga Chlorella

Cells of the green alga Chlorella kessleri Fott et Nováková use a reductive mechanism for iron acquisition. Iron-limited cells acquired iron more rapidly from a chelator with a lower stability constant for Fe3+ (hydroxyethylethylenediaminetriacetic acid (HEDTA)) than from a chelator with a higher stability constant (N,N′-di[2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED)). Furthermore, iron uptake rates decreased with increasing chelator concentrations at constant iron concentration. The negative effects of elevated HBED levels on iron uptake could be partly alleviated by the addition of Ga3+, which suggests that iron-free chelator has a negative effect on iron acquisition by competing for Fe2+ with the ferrous transport system. Furthermore, ferric reductase activity progressively decreased with increasing concentrations of both chelators (in the iron-free form). This effect was not alleviated by Ga3+ addition and was apparently caused by the direct inhibition of the reductase. Overall, we conclude that chelators with high stability constants for Fe3+ decrease iron acquisition rates by Strategy I organisms via three separate mechanisms.

scholarly journals Genetic and Physiologic Characterization of Ferric/Cupric Reductase Constitutive Mutants ofCryptococcus neoformans

1999 ◽  
Vol 67 (5) ◽  
pp. 2357-2365 ◽  
Author(s):  
Karin J. Nyhus ◽  
Eric S. Jacobson
Keyword(s):  
Hydrogen Peroxide ◽  
Iron Uptake ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Uptake System ◽  
Ferric Reductase ◽  
Pathogenic Yeast ◽  
Oxidative Stresses ◽  
Mutant Strains

ABSTRACT Cryptococcus neoformans is a pathogenic yeast that causes meningitis in immunocompromised patients. Because iron acquisition is critical for growth of a pathogen in a host, we studied the regulation of the ferric reductase and ferrous uptake system of this organism. We isolated 18 mutants, representing four independent loci, with dysregulated ferric reductase. The mutant strains had >10-fold higher than wild-type WT reductase activity in the presence of iron. Two of the strains also had >7-fold higher than WT iron uptake in the presence of iron but were not markedly iron sensitive. Both were sensitive to the oxidative stresses associated with superoxide and hydrogen peroxide. One strain exhibited only 23% of the WT level of iron uptake in the absence of iron and grew poorly without iron supplementation of the medium, phenotypes consistent with an iron transport deficiency; it was sensitive to superoxide but not to hydrogen peroxide. The fourth strain had high reductase activity but normal iron uptake; it was not very sensitive to oxidative stress. We also demonstrated that the ferric reductase was regulated by copper and could act as a cupric reductase. Sensitivity to oxidants may be related to iron acquisition by a variety of mechanisms and may model the interaction of the yeast with the immune system.

scholarly journals Genes Essential to Iron Transport in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2001 ◽  
Vol 183 (9) ◽  
pp. 2779-2784 ◽  
Author(s):  
Hirokazu Katoh ◽  
Natsu Hagino ◽  
Arthur R. Grossman ◽  
Teruo Ogawa
Keyword(s):  
Iron Uptake ◽  
Iron Transport ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Complete Medium ◽  
Iron Starvation ◽  
Transporter Family ◽  
Genes Encoding ◽  
In Cells ◽  
Pcc 6803

ABSTRACT Genes encoding polypeptides of an ATP binding cassette (ABC)-type ferric iron transporter that plays a major role in iron acquisition inSynechocystis sp. strain PCC 6803 were identified. These genes are slr1295, slr0513, slr0327, and recently reportedsll1878 (Katoh et al., J. Bacteriol. 182:6523–6524, 2000) and were designated futA1, futA2, futB, andfutC, respectively, for their involvement in ferric iron uptake. Inactivation of these genes individually or futA1and futA2 together greatly reduced the activity of ferric iron uptake in cells grown in complete medium or iron-deprived medium. All the fut genes are expressed in cells grown in complete medium, and expression was enhanced by iron starvation. ThefutA1 and futA2 genes appear to encode periplasmic proteins that play a redundant role in iron binding. The deduced products of futB and futC genes contain nucleotide-binding motifs and belong to the ABC transporter family of inner-membrane-bound and membrane-associated proteins, respectively. These results and sequence similarities among the four genes suggest that the Fut system is related to the Sfu/Fbp family of iron transporters. Inactivation of slr1392, a homologue offeoB in Escherichia coli, greatly reduced the activity of ferrous iron transport. This system is induced by intracellular low iron concentrations that are achieved in cells exposed to iron-free medium or in the fut-less mutants grown in complete medium.

scholarly journals Secreted Pyomelanin of Legionella pneumophila Promotes Bacterial Iron Uptake and Growth under Iron-Limiting Conditions

2013 ◽  
Vol 81 (11) ◽  
pp. 4182-4191 ◽  
Author(s):  
Huaixin Zheng ◽  
Christa H. Chatfield ◽  
Mark R. Liles ◽  
Nicholas P. Cianciotto
Keyword(s):  
Legionella Pneumophila ◽  
Ferrous Iron ◽  
Iron Uptake ◽  
Iron Transport ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Ferric Hydroxide ◽  
Supernatant Fraction ◽  
Content Type ◽  
Ferrous Iron Transport

ABSTRACTIron acquisition is critical to the growth and virulence ofLegionella pneumophila. Previously, we found thatL. pneumophilauses both a ferrisiderophore pathway and ferrous iron transport to obtain iron. We now report that two molecules secreted byL. pneumophila, homogentisic acid (HGA) and its polymerized variant (HGA-melanin, a pyomelanin), are able to directly mediate the reduction of various ferric iron salts. Furthermore, HGA, synthetic HGA-melanin, and HGA-melanin derived from bacterial supernatants enhanced the ability ofL. pneumophilaand other species ofLegionellato take up radiolabeled iron. Enhanced iron uptake was not observed with a ferrous iron transport mutant. Thus, HGA and HGA-melanin mediate ferric iron reduction, with the resulting ferrous iron being available to the bacterium for uptake. Upon further testing ofL. pneumophilaculture supernatants, we found that significant amounts of ferric and ferrous iron were associated with secreted HGA-melanin. Importantly, a pyomelanin-containing fraction obtained from a wild-type culture supernatant was able to stimulate the growth of iron-starved legionellae. That the corresponding supernatant fraction obtained from a nonpigmented mutant culture did not stimulate growth demonstrated that HGA-melanin is able to both promote iron uptake and enhance growth under iron-limiting conditions. Indicative of a complementary role in iron acquisition, HGA-melanin levels were inversely related to the levels of siderophore activity. Compatible with a role in the ecology and pathogenesis ofL. pneumophila, HGA and HGA-melanin were effective at reducing and releasing iron from both insoluble ferric hydroxide and the mammalian iron chelates ferritin and transferrin.

scholarly journals Conservation and Loss of a Putative Iron Utilization Gene Cluster among Genotypes of Aspergillus flavus

2021 ◽  
Vol 9 (1) ◽  
pp. 137
Author(s):  
Bishwo N. Adhikari ◽  
Kenneth A. Callicott ◽  
Peter J. Cotty
Keyword(s):  
Gene Cluster ◽  
Aspergillus Flavus ◽  
Iron Uptake ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Atmospheric Oxygen ◽  
Iron Availability ◽  
Specific Loss ◽  
Complete Deletion ◽  
Iron Utilization

Iron is an essential component for growth and development. Despite relative abundance in the environment, bioavailability of iron is limited due to oxidation by atmospheric oxygen into insoluble ferric iron. Filamentous fungi have developed diverse pathways to uptake and use iron. In the current study, a putative iron utilization gene cluster (IUC) in Aspergillus flavus was identified and characterized. Gene analyses indicate A. flavus may use reductive as well as siderophore-mediated iron uptake and utilization pathways. The ferroxidation and iron permeation process, in which iron transport depends on the coupling of these two activities, mediates the reductive pathway. The IUC identified in this work includes six genes and is located in a highly polymorphic region of the genome. Diversity among A. flavus genotypes is manifested in the structure of the IUC, which ranged from complete deletion to a region disabled by multiple indels. Molecular profiling of A. flavus populations suggests lineage-specific loss of IUC. The observed variation among A. flavus genotypes in iron utilization and the lineage-specific loss of the iron utilization genes in several A. flavus clonal lineages provide insight on evolution of iron acquisition and utilization within Aspergillus section Flavi. The potential divergence in capacity to acquire iron should be taken into account when selecting A. flavus active ingredients for biocontrol in niches where climate change may alter iron availability.

scholarly journals Characterization and partial purification of a ferrireductase from human duodenal microvillus membranes

1995 ◽  
Vol 309 (3) ◽  
pp. 745-748 ◽  
Author(s):  
H D Riedel ◽  
A J Remus ◽  
B A Fitscher ◽  
W Stremmel
Keyword(s):  
Ferrous Iron ◽  
Iron Uptake ◽  
Plasma Membranes ◽  
Ferric Iron ◽  
Reductase Activity ◽  
Nitrilotriacetic Acid ◽  
Iron Chelator ◽  
Partial Purification ◽  
Uptake System ◽  
Ammonium Sulphate Precipitation

Reduction of ferric iron in the presence of HuTu 80 cells or duodenal microvillus membranes (MVMs) was investigated. With both systems, NADH-dependent reduction of Fe3+/NTA (nitrilotriacetic acid) was demonstrated, using the ferrous iron chelator ferrozine. Uptake of Fe3+ from Fe3+/NTA by HuTu 80 cells was strongly inhibited by addition of ferrozine, indicating that Fe2+ is the substrate for the iron uptake system. With isolated plasma membranes it is shown that the reductase activity is sensitive to trypsin and incubation at 65 degrees C. The reductase activity could be extracted from the plasma membrane and partially purified by ammonium sulphate precipitation and isoelectric focusing. From the purification and inhibition characteristics we conclude that reduction of ferric iron on the surface of duodenal plasma membranes is catalysed by a membrane protein.

scholarly journals Iron Acquisition from Transferrin by Candida albicans Depends on the Reductive Pathway

2005 ◽  
Vol 73 (9) ◽  
pp. 5482-5492 ◽  
Author(s):  
Simon A. B. Knight ◽  
Gaston Vilaire ◽  
Emmanuel Lesuisse ◽  
Andrew Dancis
Keyword(s):  
Candida Albicans ◽  
Iron Uptake ◽  
Iron Reduction ◽  
Reductase Activity ◽  
Iron Acquisition ◽  
Systemic Infection ◽  
Infection Model ◽  
Cell Contact ◽  
Dialysis Bag ◽  
Reductive Pathway

ABSTRACT Host-pathogen interactions that alter virulence are influenced by critical nutrients such as iron. In humans, free iron is unavailable, being present only in high-affinity iron binding proteins such as transferrin. The fungal pathogen Candida albicans grows as a saprophyte on mucosal surfaces. Occasionally it invades systemically, and in this circumstance it will encounter transferrin iron. Here we report that C. albicans is able to acquire iron from transferrin. Iron-loaded transferrin restored growth to cultures arrested by iron deprivation, whereas apotransferrin was unable to promote growth. By using congenic strains, we have been able to show that iron uptake by C. albicans from transferrin was mediated by the reductive pathway (via FTR1). The genetically separate siderophore and heme uptake systems were not involved. FRE10 was required for a surface reductase activity and for efficient transferrin iron uptake activity in unbuffered medium. Other reductase genes were apparently up-regulated in medium buffered at pH 6.3 to 6.4, and the fre10 −/− mutant had no effect under these conditions. Experiments in which transferrin was sequestered in a dialysis bag demonstrated that cell contact with the substrate was required for iron reduction and release. The requirement of FTR1 for virulence in a systemic infection model and its role in transferrin iron uptake raise the possibility that transferrin is a source of iron during systemic C. albicans infections.

scholarly journals Genetic evidence that ferric reductase is required for iron uptake in Saccharomyces cerevisiae.

1990 ◽  
Vol 10 (5) ◽  
pp. 2294-2301 ◽  
Author(s):  
A Dancis ◽  
R D Klausner ◽  
A G Hinnebusch ◽  
J G Barriocanal
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Iron Uptake ◽  
Reductase Activity ◽  
Gene Transcript ◽  
Single Mutation ◽  
Uptake System ◽  
Ferric Reductase ◽  
Wild Type ◽  
Iron Starvation

The requirement for a reduction step in cellular iron uptake has been postulated, and the existence of plasma membrane ferric reductase activity has been described in both procaryotic and eucaryotic cells. In the yeast Saccharomyces cerevisiae, there is an externally directed reductase activity that is regulated by the concentration of iron in the growth medium; maximal activity is induced by iron starvation. We report here the isolation of a mutant of S. cerevisiae lacking the reductase activity. This mutant is deficient in the uptake of ferric iron and is extremely sensitive to iron deprivation. Genetic analysis of the mutant demonstrates that the reductase and ferric uptake deficiencies are due to a single mutation that we designate fre1-1. Both phenotypes cosegregate in meiosis, corevert with a frequency of 10(-7), and are complemented by a 3.5-kilobase fragment of genomic DNA from wild-type S. cerevisiae. This fragment contains FRE1, the wild-type allele of the mutant gene. The level of the gene transcript is regulated by iron in the same was as the reductase activity. The ferrous ion product of the reductase must traverse the plasma membrane. A high-affinity (Km = 5 microM) ferrous uptake system is present in both wild-type and mutant cells. Thus, iron uptake in S. cerevisiae is mediated by two plasma membrane components, a reductase and a ferrous transport system.

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