scholarly journals Analysis of the High-Affinity Iron Uptake System at the Chlamydomonas reinhardtii Plasma Membrane

2010 ◽  
Vol 9 (5) ◽  
pp. 815-826 ◽  
Author(s):  
Alaina Terzulli ◽  
Daniel J. Kosman
Keyword(s):  
Plasma Membrane ◽  
Chlamydomonas Reinhardtii ◽  
Iron Uptake ◽  
Ferric Iron ◽  
Iron Chelator ◽  
Multicopper Oxidase ◽  
Vital Role ◽  
Uptake System ◽  
Content Type ◽  
High Affinity

ABSTRACT Multicopper ferroxidases play a vital role in iron metabolism in bacteria, fungi, algae, and mammals. Saccharomyces cerevisiae utilizes a channeling mechanism to couple the ferroxidase activity of Fet3p to Fe3+ transport into the cell by Ftr1p. In contrast, the mechanisms by which mammals couple the ferroxidase reaction to iron trafficking is unclear. The human ferroxidases ceruloplasmin and hephaestin are twice the size of Fet3p and interact with proteins that are not expressed in fungi. Chlamydomonas FOX1 is a homolog of the human ferroxidases but likely supports iron uptake in a manner similar to that of yeast, since Chlamydomonas reinhardtii expresses a ferric iron permease homolog, FTR1. The results presented support this hypothesis. We show that FOX1 is trafficked to the plasma membrane and is oriented with its multicopper oxidase/ferroxidase domain in the exocytoplasmic space. Our analysis of FTR1 indicates its topology is similar to that of S. cerevisiae Ftr1p, with a potential exocytoplasmic iron channeling motif and two potential iron permeation motifs in membrane-spanning regions. We demonstrate that high-affinity iron uptake is dependent on FOX1 and the copper status of the cell. Kinetic inhibition of high-affinity iron uptake by a ferric iron chelator does not reflect the strength of the chelator, supporting a ferric iron channeling mechanism for high-affinity iron uptake in Chlamydomonas. Last, recombinant FOX1 (rFOX1) has been isolated in a partially holo form that exhibits the UV-visible absorbance spectrum of a multicopper oxidase and the catalytic activity of a ferroxidase.

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 restriction and the growth ofSalmonella enteritidis

1993 ◽  
Vol 110 (1) ◽  
pp. 41-47 ◽  
Author(s):  
H. Chart ◽  
B. Rowe
Keyword(s):  
Iron Uptake ◽  
Salmonella Enteritidis ◽  
Outer Membrane Proteins ◽  
Phage Type ◽  
Iron Chelator ◽  
Virulence Plasmid ◽  
Uptake System ◽  
Iron Restriction ◽  
High Affinity ◽  
Iron Uptake System

SUMMARYStrains ofSalmonella enteritidiswere examined for their ability to remove ferricions from the iron chelating agents ovotransferrin, Desferal and EDDA. Growth ofS. enteritidisphage type (PT) 4 (SE4) in trypticase soy broth containing ovotransferrin resulted in the expression of iron regulated outer membrane proteins (OMPs) of 74. 78 and 81 kDa. and unexpectedly the repression of expression of OMP C. The 38 MDa ‘mouse virulence’ plasmid was not required for the expression of the iron-regulated OMPs (IROMPs). SE4 was able to obtain iron bound to the iron chelator Desferal and EDDA without expressing a high-affinity iron uptake system. Strains ofS. enteritidisbelonging to PTs 7. 8, 13a, 23. 24 and 30 were also able to remove ferric ions from Desferal and EDDA without expressing a high-affinity iron uptake system. We conclude that strains of SE4 possess a high-affinity iron sequestering mechanism that can readily remove iron from ovotransferrin. It is likely that iron limitation, and not iron restriction, is responsible for the bacteriostatic properties of fresh egg whites.

scholarly journals Two Iron-Responsive Promoter Elements Control Expression of FOX1 in Chlamydomonas reinhardtii

2007 ◽  
Vol 6 (11) ◽  
pp. 2163-2167 ◽  
Author(s):  
Xiaodong Deng ◽  
Mats Eriksson
Keyword(s):  
Iron Deficiency ◽  
Chlamydomonas Reinhardtii ◽  
Iron Uptake ◽  
Uptake System ◽  
Promoter Elements ◽  
High Affinity ◽  
Iron Uptake System ◽  
Iron Responsive Elements

ABSTRACT FOX1 encodes an iron deficiency-induced ferroxidase involved in a high-affinity iron uptake system. Mutagenesis analysis of the FOX1 promoter identified two separate iron-responsive elements, FeRE1 (CACACG) and FeRE2 (CACGCG), between positions −87 and −82 and between positions −65 and −60, respectively, and both are needed for induced FOX1 expression under conditions of iron deficiency.

scholarly journals Regulation of Copper Metabolism by Nitrogen Utilization in Saccharomyces cerevisiae

2021 ◽  
Vol 7 (9) ◽  
pp. 756
Author(s):  
Suzie Kang ◽  
Hyewon Seo ◽  
Min-Gyu Lee ◽  
Cheol-Won Yun
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Iron Uptake ◽  
Nitrogen Starvation ◽  
Copper Metabolism ◽  
Nitrogen Utilization ◽  
Deletion Mutants ◽  
Uptake System ◽  
Wild Type ◽  
High Affinity ◽  
Uptake Activity

To understand the relationship between carbon or nitrogen utilization and iron homeostasis, we performed an iron uptake assay with several deletion mutants with partial defects in carbon or nitrogen metabolism. Among them, some deletion mutants defective in carbon metabolism partially and the MEP2 deletion mutant showed lower iron uptake activity than the wild type. Mep2 is known as a high-affinity ammonia transporter in Saccharomyces cerevisiae. Interestingly, we found that nitrogen starvation resulted in lower iron uptake activity than that of wild-type cells without downregulation of the genes involved in the high-affinity iron uptake system FET3/FTR1. However, the gene expression of FRE1 and CTR1 was downregulated by nitrogen starvation. The protein level of Ctr1 was also decreased by nitrogen starvation, and addition of copper to the nitrogen starvation medium partially restored iron uptake activity. However, the expression of MAC1, which is a copper-responsive transcriptional activator, was not downregulated by nitrogen starvation at the transcriptional level but was highly downregulated at the translational level. Mac1 was downregulated dramatically under nitrogen starvation, and treatment with MG132, which is an inhibitor of proteasome-dependent protein degradation, partially attenuated the downregulation of Mac1. Taken together, these results suggest that nitrogen starvation downregulates the high-affinity iron uptake system by degrading Mac1 in a proteasome-dependent manner and eventually downregulates copper metabolism.

scholarly journals Complex Iron Uptake by the Putrebactin-Mediated and Feo Systems in Shewanella oneidensis

2018 ◽  
Vol 84 (20) ◽  
Author(s):  
Lulu Liu ◽  
Shisheng Li ◽  
Sijing Wang ◽  
Ziyang Dong ◽  
Haichun Gao
Keyword(s):  
Iron Uptake ◽  
Iron Homeostasis ◽  
Shewanella Oneidensis ◽  
Special Role ◽  
Uptake System ◽  
Biological Processes ◽  
Content Type ◽  
Iron Uptake System ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

ABSTRACT Shewanella oneidensis is an extensively studied bacterium capable of respiring minerals, including a variety of iron ores, as terminal electron acceptors (EAs). Although iron plays an essential and special role in iron respiration of S. oneidensis, little has been done to date to investigate the characteristics of iron transport in this bacterium. In this study, we found that all proteins encoded by the pub-putA-putB cluster for putrebactin (S. oneidensis native siderophore) synthesis (PubABC), recognition-transport of Fe3+-putrebactin across the outer membrane (PutA), and reduction of ferric putrebactin (PutB) are essential to putrebactin-mediated iron uptake. Although homologs of PutA are many, none can function as its replacement, but some are able to work with other bacterial siderophores. We then showed that Fe2+-specific Feo is the other primary iron uptake system, based on the synthetical lethal phenotype resulting from the loss of both iron uptake routes. The role of the Feo system in iron uptake appears to be more critical, as growth is significantly impaired by the absence of the system but not of putrebactin. Furthermore, we demonstrate that hydroxyl acids, especially α-types such as lactate, promote iron uptake in a Feo-dependent manner. Overall, our findings underscore the importance of the ferrous iron uptake system in metal-reducing bacteria, providing an insight into iron homeostasis by linking these two biological processes. IMPORTANCE S. oneidensis is among the first- and the best-studied metal-reducing bacteria, with great potential in bioremediation and biotechnology. However, many questions regarding mechanisms closely associated with those applications, such as iron homeostasis, including iron uptake, export, and regulation, remain to be addressed. Here we show that Feo is a primary player in iron uptake in addition to the siderophore-dependent route. The investigation also resolved a few puzzles regarding the unexpected phenotypes of the putA mutant and lactate-dependent iron uptake. By elucidating the physiological roles of these two important iron uptake systems, this work revealed the breadth of the impacts of iron uptake systems on the biological processes.

scholarly journals Investigating theCampylobacter jejuniTranscriptional Response to Host Intestinal Extracts Reveals the Involvement of a Widely Conserved Iron Uptake System

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Martha M. Liu ◽  
Christine J. Boinett ◽  
Anson C. K. Chan ◽  
Julian Parkhill ◽  
Michael E. P. Murphy ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Bacterial Species ◽  
Molecular Genetic ◽  
Uptake System ◽  
Transcriptional Responses ◽  
Susceptible Animal ◽  
Susceptible Host ◽  
Altered Expression ◽  
Content Type ◽  
Iron Uptake System

ABSTRACTCampylobacter jejuniis a pathogenic bacterium that causes gastroenteritis in humans yet is a widespread commensal in wild and domestic animals, particularly poultry. Using RNA sequencing, we assessedC. jejunitranscriptional responses to medium supplemented with human fecal versus chicken cecal extracts and in extract-supplemented medium versus medium alone.C. jejuniexposed to extracts had altered expression of 40 genes related to iron uptake, metabolism, chemotaxis, energy production, and osmotic stress response. In human fecal versus chicken cecal extracts,C. jejunidisplayed higher expression of genes involved in respiration (fdhTU) and in known or putative iron uptake systems (cfbpA,ceuB,chuC, andCJJ81176_1649–1655[here designated1649–1655]). The1649–1655genes and downstream overlapping gene1656were investigated further. Uncharacterized homologues of this system were identified in 33 diverse bacterial species representing 6 different phyla, 21 of which are associated with human disease. The1649and1650(p19) genes encode an iron transporter and a periplasmic iron binding protein, respectively; however, the role of the downstream1651–1656genes was unknown. A Δ1651–1656deletion strain had an iron-sensitive phenotype, consistent with a previously characterized Δp19mutant, and showed reduced growth in acidic medium, increased sensitivity to streptomycin, and higher resistance to H2O2stress. In iron-restricted medium, the1651–1656andp19genes were required for optimal growth when using human fecal extracts as an iron source. Collectively, this implicates a function for the1649–1656gene cluster inC. jejuniiron scavenging and stress survival in the human intestinal environment.IMPORTANCEDirect comparative studies ofC. jejuniinfection of a zoonotic commensal host and a disease-susceptible host are crucial to understanding the causes of infection outcome in humans. These studies are hampered by the lack of a disease-susceptible animal model reliably displaying a similar pathology to human campylobacteriosis. In this work, we compared the phenotypic and transcriptional responses ofC. jejunito intestinal compositions of humans (disease-susceptible host) and chickens (zoonotic host) by using human fecal and chicken cecal extracts. The mammalian gut is a complex and dynamic system containing thousands of metabolites that contribute to host health and modulate pathogen activity. We identifiedC. jejunigenes more highly expressed during exposure to human fecal extracts in comparison to chicken cecal extracts and differentially expressed in extracts compared with medium alone, and targeted one specific iron uptake system for further molecular, genetic, and phenotypic study.

scholarly journals Yeast protective response to arsenate involves the repression of the high affinity iron uptake system

2013 ◽  
Vol 1833 (5) ◽  
pp. 997-1005 ◽  
Author(s):  
Liliana Batista-Nascimento ◽  
Michel B. Toledano ◽  
Dennis J. Thiele ◽  
Claudina Rodrigues-Pousada
Keyword(s):  
Iron Uptake ◽  
Uptake System ◽  
Protective Response ◽  
High Affinity ◽  
Iron Uptake System

scholarly journals Two Ways To Convert a Low-Affinity Potassium Channel to High Affinity: Control of Bacillus subtilis KtrCD by Glutamate

2020 ◽  
Vol 202 (12) ◽  
Author(s):  
Larissa Krüger ◽  
Christina Herzberg ◽  
Robert Warneke ◽  
Anja Poehlein ◽  
Janina Stautz ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Potassium Channel ◽  
Living Cell ◽  
Potassium Uptake ◽  
Selectivity Filter ◽  
Uptake System ◽  
Content Type ◽  
Apparent Affinity ◽  
High Affinity ◽  
External Potassium

ABSTRACT Potassium and glutamate are the major cation and anion, respectively, in every living cell. Due to the high concentrations of both ions, the cytoplasm of all cells can be regarded as a potassium glutamate solution. This implies that the concentrations of both ions need to be balanced. While the control of potassium uptake by glutamate is well established for eukaryotic cells, much less is known about the mechanisms that link potassium homeostasis to glutamate availability in bacteria. Here, we have discovered that the availability of glutamate strongly decreases the minimal external potassium concentration required for the highly abundant Bacillus subtilis potassium channel KtrCD to accumulate potassium. In contrast, the inducible KtrAB and KimA potassium uptake systems have high apparent affinities for potassium even in the absence of glutamate. Experiments with mutant strains revealed that the KtrD subunit responds to the presence of glutamate. For full activity, KtrD synergistically requires the presence of the regulatory subunit KtrC and of glutamate. The analysis of suppressor mutants of a strain that has KtrCD as the only potassium uptake system and that experiences severe potassium starvation identified a mutation in the ion selectivity filter of KtrD (Gly282 to Val) that similarly results in a strongly glutamate-independent increase of the apparent affinity for potassium. Thus, this work has identified two conditions that increase the apparent affinity of KtrCD for potassium, i.e., external glutamate and the acquisition of a single point mutation in KtrD. IMPORTANCE In each living cell, potassium is required for maintaining the intracellular pH and for the activity of essential enzymes. Like most other bacteria, Bacillus subtilis possesses multiple low- and high-affinity potassium uptake systems. Their activity is regulated by the second messenger cyclic di-AMP. Moreover, the pools of the most abundant ions potassium and glutamate must be balanced. We report two conditions under which the low-affinity potassium channel KtrCD is able to mediate potassium uptake at low external potassium concentrations: physiologically, the presence of glutamate results in a severely increased potassium uptake. Moreover, this is achieved by a mutation affecting the selectivity filter of the KtrD channel. These results highlight the integration between potassium and glutamate homeostasis in bacteria.

scholarly journals Iron Acquisition in Mycobacterium avium subsp. paratuberculosis

2015 ◽  
Vol 198 (5) ◽  
pp. 857-866 ◽  
Author(s):  
Joyce Wang ◽  
Jalal Moolji ◽  
Alex Dufort ◽  
Alfredo Staffa ◽  
Pilar Domenech ◽  
...  
Keyword(s):  
Mycobacterium Avium ◽  
Iron Uptake ◽  
Genomic Island ◽  
Iron Acquisition ◽  
Laboratory Data ◽  
Uptake System ◽  
Intracellular Iron ◽  
Content Type ◽  
Iron Uptake System ◽  
Environmental Bacterium

ABSTRACTMycobacterium aviumsubsp.paratuberculosisis a host-adapted pathogen that evolved from the environmental bacteriumM. aviumsubsp.hominissuisthrough gene loss and gene acquisition. Growth ofM. aviumsubsp.paratuberculosisin the laboratory is enhanced by supplementation of the media with the iron-binding siderophore mycobactin J. Here we examined the production of mycobactins by related organisms and searched for an alternative iron uptake system inM. aviumsubsp.paratuberculosis. Through thin-layer chromatography and radiolabeled iron-uptake studies, we showed thatM. aviumsubsp.paratuberculosisis impaired for both mycobactin synthesis and iron acquisition. Consistent with these observations, we identified several mutations, including deletions, inM. aviumsubsp.paratuberculosisgenes coding for mycobactin synthesis. Using a transposon-mediated mutagenesis screen conditional on growth without myobactin, we identified a potential mycobactin-independent iron uptake system on aM. aviumsubsp.paratuberculosis-specific genomic island, LSPP15. We obtained a transposon (Tn) mutant with a disruption in the LSPP15 geneMAP3776cfor targeted study. The mutant manifests increased iron uptake as well as intracellular iron content, with genes downstream of the transposon insertion (MAP3775ctoMAP3772c[MAP3775-2c]) upregulated as the result of a polar effect. As an independent confirmation, we observed the same iron uptake phenotypes by overexpressingMAP3775-2cin wild-typeM. aviumsubsp.paratuberculosis. These data indicate that the horizontally acquired LSPP15 genes contribute to iron acquisition byM. aviumsubsp.paratuberculosis, potentially allowing the subsequent loss of siderophore production by this pathogen.IMPORTANCEMany microbes are able to scavenge iron from their surroundings by producing iron-chelating siderophores. One exception isMycobacterium aviumsubsp.paratuberculosis, a fastidious, slow-growing animal pathogen whose growth needs to be supported by exogenous mycobacterial siderophore (mycobactin) in the laboratory. Data presented here demonstrate that, compared to other closely relatedM. aviumsubspecies, mycobactin production and iron uptake are different inM. aviumsubsp.paratuberculosis, and these phenotypes may be caused by numerous deletions in its mycobactin biosynthesis pathway. Using a genomic approach, supplemented by targeted genetic and biochemical studies, we identified that LSPP15, a horizontally acquired genomic island, may encode an alternative iron uptake system. These findings shed light on the potential physiological consequence of horizontal gene transfer inM. aviumsubsp.paratuberculosisevolution.

scholarly journals Dual Regulation of the Arabidopsis High-Affinity Root Iron Uptake System by Local and Long-Distance Signals

2003 ◽  
Vol 132 (2) ◽  
pp. 796-804 ◽  
Author(s):  
Grégory A. Vert ◽  
Jean-François Briat ◽  
Catherine Curie
Keyword(s):  
Iron Uptake ◽  
Uptake System ◽  
Long Distance ◽  
High Affinity ◽  
Iron Uptake System
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