OXYGEN CONSUMPTION ASSOCIATED WITH FERRIC REDUCTASE ACTIVITY AND IRON UPTAKE BY IRON-LIMITED CELLS OF CHLORELLA KESSLERI (CHLOROPHYCEAE)

2001 ◽  
Vol 37 (3) ◽  
pp. 393-399 ◽  
Author(s):  
Jocelyn K. Middlemiss ◽  
Andrea M. Anderson ◽  
Chad W. Stratilo ◽  
Harold G. Weger
Keyword(s):  
Oxygen Consumption ◽  
Iron Uptake ◽  
Reductase Activity ◽  
Ferric Reductase ◽  
Chlorella Kessleri

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 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.

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.

scholarly journals Two distinctly regulated genes are required for ferric reduction, the first step of iron uptake in Saccharomyces cerevisiae.

1994 ◽  
Vol 14 (5) ◽  
pp. 3065-3073 ◽  
Author(s):  
E Georgatsou ◽  
D Alexandraki
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Iron Uptake ◽  
Reductase Activity ◽  
Transcriptional Level ◽  
Gene Products ◽  
Ferric Reductase ◽  
Ferrous Ions ◽  
Temporal Regulation ◽  
Iron Deprivation ◽  
Total Membrane

Iron uptake in Saccharomyces cerevisiae involves at least two steps: reduction of ferric to ferrous ions extracellularly and transport of the reduced ions through the plasma membrane. We have cloned and molecularly characterized FRE2, a gene which is shown to account, together with FRE1, for the total membrane-associated ferric reductase activity of the cell. Although not similar at the nucleotide level, the two genes encode proteins with significantly similar primary structures and very similar hydrophobicity profiles. The FRE1 and FRE2 proteins are functionally related, having comparable properties as ferric reductases. FRE2 expression, like FRE1 expression, is induced by iron deprivation, and at least part of this control takes place at the transcriptional level, since 156 nucleotides upstream of the initiator AUG conferred iron-dependent regulation when fused to a heterologous gene. However, the two gene products have distinct temporal regulation of their activities during cell growth.

Two distinctly regulated genes are required for ferric reduction, the first step of iron uptake in Saccharomyces cerevisiae

1994 ◽  
Vol 14 (5) ◽  
pp. 3065-3073
Author(s):  
E Georgatsou ◽  
D Alexandraki
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Iron Uptake ◽  
Reductase Activity ◽  
Transcriptional Level ◽  
Gene Products ◽  
Ferric Reductase ◽  
Ferrous Ions ◽  
Temporal Regulation ◽  
Iron Deprivation ◽  
Total Membrane

Iron uptake in Saccharomyces cerevisiae involves at least two steps: reduction of ferric to ferrous ions extracellularly and transport of the reduced ions through the plasma membrane. We have cloned and molecularly characterized FRE2, a gene which is shown to account, together with FRE1, for the total membrane-associated ferric reductase activity of the cell. Although not similar at the nucleotide level, the two genes encode proteins with significantly similar primary structures and very similar hydrophobicity profiles. The FRE1 and FRE2 proteins are functionally related, having comparable properties as ferric reductases. FRE2 expression, like FRE1 expression, is induced by iron deprivation, and at least part of this control takes place at the transcriptional level, since 156 nucleotides upstream of the initiator AUG conferred iron-dependent regulation when fused to a heterologous gene. However, the two gene products have distinct temporal regulation of their activities during cell growth.

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.

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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