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Clostridioides (formerly Clostridium) difficile is a leading cause of infectious diarrhea associated with antibiotic therapy. The ability of this anaerobic pathogen to acquire enough iron to proliferate under iron limitation conditions imposed by the host largely determines its pathogenicity. However, since high intracellular iron catalyzes formati...
FurC (PerR, Peroxide Response Regulator) from Anabaena sp. PCC 7120 (also known as Nostoc sp. PCC 7120) is a master regulator engaged in the modulation of relevant processes including the response to oxidative stress, photosynthesis and nitrogen fixation. Previous differential gene expression analysis of a furC-overexpressing strain (EB2770FurC) al...
Fruit-tree rootstock selection is a challenge under a scenario of growing environmental stresses in which the soil and climate are greatly affected. Salinization is an increasing global process that severely affects soil fertility. The selection of rootstocks with the ability to tolerate salt stress is essential. Excised root cultures may be an exc...
Ferric uptake regulator (FUR) proteins are involved in the regulation of genes related to metal homeostasis and the oxidative stress response in most prokaryotes. The cyanobacterium Anabaena sp. PCC 7120 contains three FUR paralogs: FurA, FurB, and FurC. Previous studies demonstrated that overexpression of FurA and FurB increased oxidative stress t...
FurA is a multifunctional regulator in cyanobacteria that contains five cysteines, four of them arranged into two CXXC motifs. Lack of a structural zinc ion enables FurA to develop disulfide reductase activity. In vivo, FurA displays several redox isoforms, and the oxidation state of its cysteines determines its activity as regulator and its abilit...
FurC (PerR) from Anabaena sp. PCC7120 was previously described as a key transcriptional regulator involved in setting off the oxidative stress response. In the last years, the cross‐talk between oxidative stress, iron homeostasis and nitrogen metabolism is becoming more and more evident. In this work, the transcriptome of a furC‐overexpressing stra...
Proteins belonging to the FUR (ferric uptake regulator) family are the cornerstone of metalloregulation in most prokaryotes. Although numerous reviews have been devoted to these proteins, these reports are mainly focused on the Fur paralog that gives name to the family. In the last years, the increasing knowledge on the other, less ubiquitous membe...
2‐oxoglutarate is a central metabolite that acts as a signaling molecule informing about the status of the carbon/nitrogen balance of the cell. In recent years, some transcriptional regulators and even two‐component systems have been described as 2‐oxoglutarate sensors. In the nitrogen‐fixing cyanobacterium Anabaena sp. PCC 7120, two master regulat...
FurA (Ferric Uptake Regulator) from the cyanobacteria Anabaena sp. PCC 7120 is a transcriptional regulator that controls not only iron homeostasis but also other important cellular processes such as oxidative stress response, nitrogen metabolism or cell morphology. Furthermore FurA has been proposed to act as a redox sensor protein, due to its disu...
Significance:
The successful adaptation of microorganisms to ever-changing environments depends, to a great extent, on their ability to maintain redox homeostasis. To effectively maintain the redox balance, cells have developed a variety of strategies mainly coordinated by a battery of transcriptional regulators through diverse mechanisms. Recent...
A 3D representation of the filamentous cyanobacteria Anabaena. In the latest issue, Sein-Echaluce et al. report on the molecular basis for the integration of environmental signals by FurB from Anabaena sp. PCC 7120; for details see pages 151–168.
FUR proteins are among the most important families of transcriptional regulators in prokaryotes, often behaving as global regulators. In the cyanobacterium Anabaena PCC 7120 FurB (Zur) controls zinc and redox homeostasis through the repression of target genes in a zinc-dependent manner. In vitro , nonspecific binding of FurB to DNA elicits protecti...
Cyanobacteria are the only prokaryotes that perform oxygenic photosynthesis. Cyanobacteria populate an ample range of diverse and extreme habitats and contribute significantly to the global photosynthetic primary productivity and the fixation of atmospheric nitrogen. Some filamentous strains are capable of cell differentiation, which is unique amon...
In the nitrogen-fixing heterocyst-forming cyanobacterium Anabaena sp. PCC 7120, the ferric uptake regulator FurA plays a global regulatory role. Failures to eliminate wild-type copies of furA gene from the polyploid genome suggest essential functions. In the present study, we developed a selectively regulated furA expression system by the replaceme...
Figure A: Expression of FurA results essential to the growth of Anabaena sp. under standard culture conditions. Figure B: Fold changes in the expression of FurA direct targets in the furA-turning off strain Anabaena sp. AGcoaRFurA after cobalt/zinc deprivation as compared with the wild-type PCC 7120 strain under the same growth condition, as result...
Iron-containing metalloproteins are the main cornerstones for efficient electron transport in biological systems. The abundance and diversity of iron-dependent proteins in cyanobacteria makes those organisms highly dependent of this micronutrient. To cope with iron imbalance, cyanobacteria have developed a survey of adaptation strategies that are s...
Aims:
The ferric uptake regulator (Fur) is the main transcriptional regulator of genes involved in iron homeostasis in most prokaryotes. FurA from Anabaena sp. PCC 7120 contains five cysteine residues, four of them arranged in two redox-active CXXC motifs. The protein needs not only metal but also reducing conditions to remain fully active in vitr...
HCH factories, and the waste dumpsites associated to its production, have become a global environmental concern, and their runoff could pollute ground and surface waters with high levels of the pollutant. In this study, the influence of lindane (γ-HCH) on microcystin production has been investigated in Microcystis aeruginosa PCC7806. This toxic cya...
The human Apoptosis Inducing Factor (hAIF) is a bifunctional NAD(P)H-dependent flavoreductase involved in both mitochondrial energy metabolism and caspase-independent cell death. Even though several studies indicate that both functions are redox controlled by NADH binding, the exact role of hAIF as a reductase in healthy mitochondria remains unknow...
Currently, the presence of several pharmaceuticals and other organic compounds called 'emerging' contaminants has increased in water bodies. These compounds do not need to persist in the environment to cause negative effects because they are continuously introduced. Hence, assessing the effects of these compounds on aquatic ecosystems is essential....
The growth and synthesis of microcystin in Microcystis ruginosa PCC7806 was studied in cells grown in the presence of NaCl or with sucrose. The saline stress caused a decrease in the transcript levels of mcyD, one of the genes involved in microcystin synthesis, which was correlated with a decrease in the content of microcystin-LR in the cells. The...
The identification of protein binding sites in promoter sequences is a key problem to understand and control regulation in biochemistry and biotechnological processes. We use a computational method to analyze promoters from a given genome. Our approach is based on a physical model at the mesoscopic level of protein-DNA interaction based on the infl...
The physical modelization of biomolecules requires a careful choice of the scale of work depending on the problem we wish to study. All-atom simulations allow an accurate description of the system but within small time scales and severe size limitations subject to the available computational power. Coarse-grained models gather groups of atoms in po...
The physical modelization of biomolecules requires a careful choice of the scale of work depending on the problem we wish to study. All-atom simulations allow an accurate description of the system but within small time scales and severe size limitations subject to the available computational power. Coarse-grained models gather groups of atoms in po...
This work proposes an educational experiment carried out with three generations of pupils from a Biotechnology Degree. Students were divided into groups of six, and each group had to a) detect a problem or deficiency in any aspect of daily life related to biotechnology, b) examine existing solutions today, and c) propose new opportunities to innova...
Cyanobacterial metabolism relies on the activity of many enzymes and other proteins containing metal-rich cofactors that are absent in nonphotosynthetic organisms. Most of those micronutrients play key roles in or are associated to photosystems, respiratory electron transport chains and many enzymes involved in nitrogen metabolism. Since metal home...
Unlabelled:
Cyanobacterial FurA works as a global regulator linking iron homeostasis to photosynthetic metabolism and the responses to different environmental stresses. Additionally, FurA modulates several genes involved in redox homeostasis and fulfills the characteristics of a heme-sensor protein whose interaction with this cofactor negatively a...
In Anabaena sp. PCC 7120, FurA is a global transcriptional regulator whose expression is strongly induced by NtcA in proheterocysts and remains stably expressed in mature heterocysts. In the present study, overexpression of furA partially suppressed heterocyst differentiation by impairing morphogenesis at an early stage. Recombinant purified FurA s...
A real-time RT-PCR analysis of the transcriptional response to phosphate availability of the mcyD gene and microcystin-LR synthesis in Microcystis aeruginosa PCC7806 revealed that no significant changes were observed in the relative quantification of mcyD under excess phosphate (N/P = 1:1), whereas in deficiency of this nutrient (N/P = 40:1), a ste...
The occurrence of free-living amoebae (FLA) was investigated in 83 water samples from reservoirs and water treatment plants, with culture positive in 64 of them (77.1%). PCRs of partial 18S rRNA gene and ITS region were performed in order to identify amoebae isolates and the presence of Legionella pneumophila, Mycobacterium spp., Pseudomonas spp an...
Changes in water use and anthropogenic activity have major impacts on the quality of natural aquatic ecosystems, water distribution and wastewater plants. One of the main problems is the presence of some pathogenic microorganisms that are resistant to disinfection procedures when they are hosted by free living amoeba and that in many cases are hard...
Knowledge on the regulatory mechanisms controlling iron homeostasis in cyanobacteria is limited. In Anabaena sp. PCC 7120, the ferric uptake regulator FurA is a constitutive and essential protein whose expression is induced under iron deprivation. Our previous analyses have shown that this protein acts as a global transcriptional regulator, control...
The transcriptional repressor Fur (ferric uptake regulator) is one of the most important switches regulating prokaryotic iron metabolism. Cyanobacterial FurA binds heme in the micromolar concentration range and this interaction negatively affects its in vitro DNA binding ability in a concentration-dependent manner. Using site-directed mutagenesis a...
DNA-binding proteins are fundamental elements in cells of all living organisms. They participate in essential cellular processes like DNA replication, transcription, recombination and repair, while some of them constitute valuable tools in routine genetic engineering manipulations. Nucleases, polymerases, topoisomerases, transcriptional factors and...
In Anabaena sp. PCC 7120, the ferric uptake regulator FurA is a constitutive and essential protein whose expression is induced under iron deprivation. In the present study we analyzed the impact of FurA overexpression and iron availability on the transcriptional modulation of a broad range of Anabaena iron uptake, transport, storage, and cellular i...
In this study, quantitative real time RT-PCR has been used to monitor changes in the levels of transcripts encoding mcyD in Microcystis aeruginosa PCC7806 under oxidative agents and different conditions of light intensity. Microcystin content has also been determined in the same stressed cell aliquots. Our results corroborate the fact that changes...
The binding affinity of NtcA towards promoter regions of the microcystin gene cluster from Microcystis aeruginosa PCC 7806 has been analyzed by band-shift assay (EMSA). The key nitrogen transcriptional regulator exhibits affinity for two fragments of the bidirectional mcyDA promoter, as well as for promoter regions of mcyE and mcyH. The presence of...
Ferric uptake regulation (Fur) proteins are prokaryotic transcriptional regulators that integrate signaling of iron metabolism and oxidative stress responses with several environmental stresses. In photosynthetic organisms, Fur proteins regulate many genes involved in photosynthesis, nitrogen metabolism and other key processes. Also, Fur triggers t...
The interplay between Fur (ferric uptake regulator) proteins and small, non-coding RNAs has been described as a key regulatory loop in several bacteria. In the filamentous cyanobacterium Anabaena sp. PCC 7120, a large dicistronic transcript encoding the putative membrane protein Alr1690 and an α-furA RNA is involved in the modulation of the global...
The influence of environmental factors on microcystin production by toxic cyanobacteria has been extensively studied. However, the effect of nitrogen on the synthesis of this toxin remains unclear because of the literature contradictory data. The aim of this work was to determine how nitrate affects the transcriptional response of mcyD gene and the...
Previous genomic analyses of the filamentous nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120 have identified three ferric uptake regulator (Fur) homologs with low sequence identities and probably different functions in the cell. FurA is a constitutive protein that shares the highest homology with Fur from heterotrophic bacteria and appears to...
Fur proteins are global prokaryotic transcriptional regulators. Functional studies of FurA from the cyanobacterium Anabaena sp. PCC 7120 evidenced the influence of the redox environment in the activity of the regulator and its ability to aggregate through disulphide bridges. Atomic force microscopy allows single-molecule imaging and monitorization...
Fur proteins are global regulators present in all prokaryotes. In Anabaena sp. PCC 7120 FurA controls iron uptake and modulates an important set of genes related primarily to photosynthesis, nitrogen metabolism and oxidative stress defense. Expression of furA is tuned by the cis-acting antisense alpha-furA RNA that is co-transcribed with the outer-...
Engineering of DNA-binding domains of regulatory proteins aimed to control gene expression requires a deep knowledge of protein–DNA interactions acquired from structural data on purified species. Most DNA-binding proteins work as dimers establishing multiple protein–protein contacts mainly driven by hydrophobic interactions, being its cleansing a d...
Heterocyst differentiation and its spacing pattern formation in filamentous nitrogen-fixing cyanobacteria occur as result of multiple signals and the influence of several regulators. Previous studies have suggested a transcriptional regulatory connection between iron and nitrogen metabolism in Anabaena sp., since the ferric uptake regulator FurA bo...
Microcystins are toxins produced by some strains of cyanobacteria. Several methods have been developed to allow the quantification of microcystins, which are mainly endotoxins. Among those methods, the protein phosphatase inhibition assay is a good candidate as a screening method because of its sensitivity, simplicity and specificity. In this work...
Se propone un método para la determinación de las microcistinas intracelulares y disueltas en muestras de aguas no potabilizadas. Los resultados obtenidos con el método propuesto, basado en la inhibición de fosfatasa, se han comparado con los obtenidos mediante HPLC-UV. Además, se ha demostrado que dicho protocolo evita el efecto de potenciales int...
The structural organization of the mitochondrial respiratory complexes as four big independently moving entities connected by the mobile carriers CoQ and cytochrome c has been challenged recently. Blue native gel electrophoresis reveals the presence of high-molecular-weight bands containing several respiratory complexes and suggesting an in vivo as...
Fur (ferric uptake regulator) is a prokaryotic transcriptional regulator that controls a large number of genes mainly related to iron metabolism. Several Fur homologues with different physiological roles are frequently found in the same organism. The genome of the filamentous cyanobacterium Anabaena (Nostoc) sp. PCC 7120 codes for three different f...
Microcystins are toxins produced by cyanobacteria that entail serious health and environmental problems. They are cyclic heptapeptides synthesized via a mixed polyketide synthase/non-ribosomal peptide synthetase system called microcystin synthetase. Environmental and nutritional factors that trigger microcystin synthesis are still debated and this...
The physiological role of microcystin-LR is still under discussion, and since binding of microcystin-LR to proteins different from their main cellular targets was described, we have performed experiments in order to explore this interaction. A non-specific interaction of microcystin-LR with a variety of soluble proteins in vitro is disrupted when u...
Two ferredoxin-dependent enzymes involved in the photosynthetic assimilation of nitrogen, nitrite reductase (EC 1.7.7.1) and glutamate synthase (EC 1.4.7.1) from Chlorella fusca have been shown to use either ferredoxin or flavodoxin (from the same organism) as electron donor. Nitrite reductase showed Km, values of 13.8 ± 0.9 μM for ferredoxin and 3...
Nitrogen signalling in cyanobacteria involves a complex network in which the availability of iron plays an important role. In the nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120, iron uptake is controlled by FurA, while NtcA is the master regulator of nitrogen metabolism and shows a mutual dependence with HetR in the first steps of heterocyst...
La OMS (Organización Mundial de la Salud) ha establecido un nivel guía máximo de microcistina en aguas para consumo humano de 1 µg/L. Esta recomendación se ha incorporado en la legislación espa-ñola a través del R.D 140/2003 para aguas emergentes de potabilizadoras con sospecha de eutrofiza-ción. Existen varios métodos para la detección de microcis...
The DNA-binding protein from stationary phase (Dps) protein family plays an important role in protecting microorganisms from oxidative and nutritional stresses. In silico analysis of the promoter region of alr3808, a dpsA homologue from the cyanobacterium Nostoc sp. PCC7120 shows putative iron-boxes with high homology with those recognized by FurA...
Fur (ferric uptake regulator) proteins are principally responsible for maintaining iron homeostasis in prokaryotes. Iron is usually a scarce resource. Its limitation reduces photosynthetic rates and cell growth in cyanobacteria in general and especially in cyanobacteria that are fixing dinitrogen, a process that requires the synthesis of numerous p...
Fur (ferric uptake regulator) proteins are global regulatory proteins involved in the maintenance of iron homeostasis. They recognize specific DNA sequences denoted iron boxes. It is assumed that Fur proteins act as classical repressors. Under iron-rich conditions, Fur dimers complexed with ferrous ions bind to iron boxes, preventing transcription....
The Fur (ferric uptake regulator) protein is a global regulator in most prokaryotes that controls a large number of genes. Fur is a classical repressor that uses ferrous iron as co-repressor and binds to specific DNA sequences (iron boxes) as a dimer. Three different genes coding for Fur homologues have been identified in Anabaena sp. PCC 7120. Fur...
Promoter regions of the mcy operon from Microcystis aeruginosa PCC7806, which is responsible for microcystin synthesis in this organism, exhibit sequences that are similar to the sequences recognized by Fur (ferric uptake regulator). This DNA-binding protein is a sensor of iron availability and oxidative stress. In the presence of Fe(2+), a dimer o...
Ferredoxin-NADP+ reductase (FNR, EC I.18.1.2) from the green algae Chlorella fusca Shihira et Kraus 211–15, was purified to homogeneity. The molecular mass was 36.8 kDa as determined by SDS-polyacrylamide gel electrophoresis. The enzyme exhibits the typical spectrum of a flavoprotein with an absorption maximum at 459 nm and an A273/459 ratio of 7.2...
Ferric uptake regulator (Fur) proteins are widely recognized as repressors that in many prokaryotes regulate a large number of genes involved in iron homeostasis and oxidative stress response. In our study, we were able to identify the complete sequence of the fur gene from Microcystis aeruginosa using inverse-polymerase chain reaction. DNA sequenc...
Ferric uptake regulation (Fur) proteins are prokaryotic transcriptional regulators that integrate iron metabolism with several environmental stress responses. The regulatory network that governs Fur proteins is rather complex. Control at several stages from gene transcription to post-translational binding of different ligands has been reported in F...
Fur (ferric uptake regulator) is a key bacterial protein that regulates iron acquisition and its storage, and modulates the expression of genes involved in the response to different environmental stresses. Although the protein is involved in several regulation mechanisms, and members of the Fur family have been identified in pathogen organisms, the...
Heme is an iron-containing cofactor that aside from serving as the active group of essential proteins is a key element in the control of many molecular and cellular processes. In prokaryotes, the family of Fur (ferric uptake regulator) proteins governs processes essential for the survival of microorganims such as the iron homeostasis. We show that...
DNA sequence analysis of the Anabaena sp. PCC7120 genome confirmed the presence of three open reading frames (all1691, all2473 and alr0957) containing the histidine-rich region characteristic of the Fur family. The genes coding for the three Fur proteins were cloned and overexpressed in Escherichia coli. The overexpression products, called FurA, Fu...
DNA sequence analysis of the Anabaena sp. PCC7120 genome confirmed the presence of three open reading frames (all1691, all2473 and alr0957) containing the histidine-rich region characteristic of the Fur family. The genes coding for the three Fur proteins were cloned and overexpressed in Escherichia coli. The overexpression products, called FurA, Fu...
On Feb 23, 2007 this sequence version replaced gi:48479085.
Plastocyanin and cytochrome c6 from the green alga Scenedesmus vacuolatus were immunoquantified in cells grown under different concentrations of copper and iron. Plastocyanin expression was constitutive, its synthesis was not significantly affected by iron availability, and increases with copper availability. On the contrary, cytochrome c6 synthesi...
Quantification of the iron-nutritional status of phytoplankton is of great interest not only for the study of oceans but also for fresh waters. Flavodoxin is a small flavoprotein proposed as a marker for iron deficiency, since it is induced as a consequence of iron deprivation, replacing the iron-sulphur protein ferredoxin. Flavodoxin and ferredoxi...
The purification of a protein is the essential initial step in the study of its physical and biological properties and is one of the most common procedures in biochemistry. This article describes a method for teaching purification skills through the partial isolation of ferredoxin-NADP+ reductase and ferredoxin from a single cell batch. The method...
Flavodoxin and ferredoxin can be used as molecular markers for determination of biolimitation of iron in phytoplankton. Two
ELISA tests have been used for determination of flavodoxin and ferredoxin respectively in samples from three endorheic
lagoons.RésuméLa flavodoxine et la ferredoxine peuvent être utilisées comme marqueurs moléculaires pour dét...
Quantification of the iron nutritional status of phytoplankton is of great interest not only for the study of the oceans but also for fresh waters. Flavodoxin is a small flavoprotein proposed as a molecular marker for iron stress, since it is induced as a consequence of iron deprivation, replacing the iron-sulphur protein ferredoxin. Flavodoxin and...
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 disul...
Root tips of Fe-deficient and Fe-sufficient sugar beet plants grown in hydroponics have been used to study the changes in the amount and activity of the cytosolic enzyme phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31). Phosphoenolpyruvate carboxylase activity in extracts of the yellow Fe-deficient root tips was, at pH 7.3, 30-fold higher (when...
Capacitation of spermatozoa, a complex process occurring after sperm ejaculation, is required to produce fertilization of the oocyte in vivo and in vitro. Although this process results from a poorly understood series of morphological and molecular events, protein tyrosine phosphorylation has been associated with sperm capacitation in several mammal...
Fur (Ferric uptake regulator) is a DNA-binding protein which represses the transcription of iron-regulated promoters using Fe2+ as a cofactor. In Gram negative bacteria, fur controls the expression of toxins and virulence factors when facing iron-stress. Iron is a key element limiting the growth and proliferation of phytoplankton. We have cloned th...
The purification of isolated and intact heterocysts is an essential step in the study and characterisation of their specific proteins. Therefore, a method for very successful heterocyst isolation from filamentous cyanobacteria, as monitored by measuring the presence of ferredoxin-NADP+ reductase activity during the isolation procedure has been deve...
En muestras colectadas en la proliferación detectada en otoño del año 2000 en La Estanca de Alcañiz (Teruel) se ha llevado a cabo la amplificación de regiones promotoras de genes descritas en el operón mcy de Microcystis aeruginosa PCC 7806. El resultado ha mostrado la amplificación de tres regiones con un considerable grado de homología con el cit...
Se ha purificado una nueva proteína del alga verde Scenedesmus vacuolatus. Esta proteína presenta reactividad cruzada con los anticuerpos de plastocianina, tiene un peso molecular aparente de 42 kDa, un punto isoelétrico acídico. Esta proteína parece verse afectada por la disponibilidad de cobre, y se expresa coordinadamente con la plastocianina.
Enzyme activity determinations and Western and Northern blot analyses have shown the presence of two catalytically different glyceraldehyde-3-phosphate dehydrogenases (GAPDH) in both vegetative cells and heterocysts of several N(2)-fixing Anabaena strains: (a) the gap2-encoded NAD(P)-dependent GAPDH2 (EC 1.2.1.59), the enzyme involved in the photos...
Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein, which translocates to the nucleus during apoptosis and causes chromatin condensation and large scale DNA fragmentation. Here we report the biochemical characterization of AIF's redox activity. Natural AIF purified from mitochondria and recombinant AIF purified from bacteria (AIFDelta1...
A gene coding for a Fur (ferric uptake regulation) protein from the cyanobacterium Anabaena PCC 7119 has been cloned and overexpressed in Escherichia coli. DNA sequence analysis confirmed the presence of a 151-amino-acid open reading frame that showed homology with the Fur proteins reported for the unicellular cyanobacteria Synechococcus 7942 and S...
A complex between ferredoxin-NADP+ reductase (EC 1.18.1.2.) and phycobiliproteins has been isolated from Anabaena PCC 7119. Two proteins of 18 and 12.5 kDa bound to FNR have been sequenced at the amino terminal segment. The 18 kDa polypeptide has been identified as the c-phycocyanin alpha chain, a subunit from the peripheral rods of phycobilisomes....
[2Fe-2S] ferredoxins, also called plant-type ferredoxins, are low-potential redox proteins that are widely distributed in biological systems. In photosynthesis, the plant-type ferredoxins function as the central molecule for distributing electrons from the photolysis of water to a number of ferredox-independent enzymes, as well as to cyclic photoph...
Under conditions of iron stress, many organisms replace the common iron-sulfur redox protein ferredoxin with flavodoxin, a functionally equivalent, non-iron-containing protein. These 2 proteins have been proposed to be indicators of iron nutritional status in marine phytoplankton, but little is known of their expression and regulation. This study c...
A soluble monoheme c-type cytochrome c6 was isolated from the marine diatom Thalassiosira weissflogii. The isolated protein shows an apparent molecular weight of 13 kDa and an isoelectric point of 3.6 in the ferric form and 3.8 in the ferrous form. The visible spectrum of the reduced cytochrome c6 is typical of a c-type heme protein, with maxima at...
Two ferredoxin-dependent enzymes involved in the pho-tosynthetic assimilation of nitrogen, nitrite reductase (EC 1.7.7.1) and glutamate synthase (EC 1.4.7.1) from ChZo-rellu fusca have been shown to use either ferredoxin or flavodoxin (from the same organism) as electron donor. Nitrite reductase showed K,,, values of 13.8 & 0.9 pkf for ferredoxin a...
A c-type monohaem, cytochrome c6was isolated from a soluble extract of the green alga Chlorella fusca. The isolated protein shows an apparent molecular mass of 10 kDa by SDS-PAGE, but behaves as a dimer of 20.3 kDa in gel-filtration; the isoelectric point is 3.6. The N-terminal sequence shows high identity with other green algae cytochromes c6. The...
A soluble monoheme c–type cytochrome c
6 has been isolated from the cyanobacterium Anabaena PCC 7119. It is a basic protein, with a molecular mass of 9.7 kDa, which accepts electrons from Anabaena ferredoxin in the ferredoxin-NADP+reductase-dependent NADPH cytochrome c reductase activity assay. The turnover of the reaction has an optimum pH at 7.5....
The expression of ferredoxin-NADP+ reductase (FNR) from Anabaena sp. PCC 7119 in heterocysts and vegetative cells has been quantified. Specific reductase activity in heterocysts was approximately 10 times higher than in vegetative cells, corresponding to the increased FNR protein content. This was confirmed by immunoquantification of the FNR protei...
The controversy surrounding the question of whether iron limits phytoplankton production in high-nutrient, low-chlorophyll regions of the world's oceans has stimulated research on numerous fronts, including the search for diagnostic indicators of phytoplankton iron nutritional status. Flavodoxin (Fly), an iron-independent protein capable of catalyz...
