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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hexagonal bilayer haemoglobin molecule from Nereis virens has been investigated in a comparative study using several different negative stain electron microscopical specimen preparations (i.e. by conventional adsorption to continuous carbon support films, by the negative staining-carbon film technique and by negative staining across the holes of holey carbon support films with air-drying and rapid freezing/cryo-negative staining). The benefits and limitations of these different approaches are indicated, with the overall conclusion that negative staining with ammonium molybdate across holes creates the best possibilities for molecular imaging, and also has the potential for the creation of two-dimensional (2D) crystals/arrays at the fluid-air interface. Of the different negative staining procedures presented, cryo-negative staining reveals the greatest details of N. virens haemoglobin. This is exemplified by the direct visualisation of the central linker-assembly within the haemoglobin molecule, a structural feature less clearly defined by the other negative staining techniques. A discoidal lipoprotein molecule (diameter 30-60nm; thickness ca 8nm) has been detected in N. virens, which represents the first documented account of an annelid haemolymph lipoprotein. The biological implications of this lipoprotein for lipid transport remain to be established. The presence of a low concentration of ferritin molecules in N. virens haemolymph is also shown, assisted by the formation of small 2D ferritin arrays in negatively stained specimens prepared across holes.
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PMID:Transmission electron microscopical studies on some haemolymph proteins from the marine polychaete Nereis virens. 1116 80

In order to measure the effects of HFE (haemochromatosis) upon iron uptake, stable expression of wild-type and C282Y, H63D and S65C mutant HFE cDNA was established in HEK 293 cells. Control cells were transfected with empty vector. Expression of HFE mRNA and protein was detected in the cell lines transfected with HFE cDNA, but not in the control cell line. The ferritin concentration in wild-type cells cultured in 40 microM ferric ammonium citrate was 69% of that in control cells and 81% of that in C282Y cells. The ferritin concentration in H63D cells was intermediate between wild-type and C282Y and the ferritin concentration in S65C cells was similar to wild-type cells. Uptake of transferrin-iron in wild-type, C282Y and control cells was measured over 45 min. The Hill coefficients for transferrin-iron uptake were similar. The V(max) for transferrin-iron uptake in wild-type cells was 59.5% of control cells and 69.5% of C282Y cells. Estimates of K(m) were 232 nM for wild-type cells, 338 nM for C282Y cells and 570 nM for controls. Transferrin receptor levels were lowered, but not significantly, in the HFE transfected cells. The results show that HFE reduces transferrin-iron uptake, probably as an uncompetitive inhibitor.
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PMID:The effects of wild-type and mutant HFE expression upon cellular iron uptake in transfected human embryonic kidney cells. 1133 95

Iron that is not bound to storage proteins can catalyse the generation of toxic hydroxyl radicals. Iron can be released from brain storage proteins by hypoxic conditions, such as those that accompany stroke, and the situation can be compounded by iron released from hemoglobin in extravasated blood cells. Despite the neurotoxicity of iron, there is little quantitative data concerning the spatio-temporal extent of its toxicity in vivo. The present study measures the effects of a pathologically relevant concentration of iron (1.0 mM) on neuronal death and on ferritin expression in vivo. Injection of iron (1 microl ferric ammonium citrate) into rat parietal cortex resulted in 7.9-fold more ferritin-labeled cells than did control injections of ammonium citrate at 1 day post-injection. This elevated expression continued for at least 1 week. One day after injection, the mean number of Fluoro-Jade-labeled degenerating neurons in 100 microm sections passing through the center of ferric ammonium citrate injection sites was 664+/-64. This value was 4.5-fold higher than at ammonium citrate injection sites, and this difference increased to 56-fold by day three. By 5 days post-injection, few dying neurons were observed at the control sites, but neurodegeneration continued beyond a week at the iron-injected sites. Thus, iron released during a brief episode of hypoxia-ischemia or during a stroke may be neurotoxic for a protracted period. Therefore, our findings indicate that it may be beneficial to target iron-induced peroxidation throughout the first few weeks following an intracerebral hemorrhage or an hypoxic-ischemic episode.
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PMID:Quantitative analysis of cell death and ferritin expression in response to cortical iron: implications for hypoxia-ischemia and stroke. 1143 Sep 1

It has long been assumed that iron regulates the turnover of ferritin, but evidence for or against this idea has been lacking. This issue was addressed using rat hepatoma cells with characteristics of hepatocytes subjected to a continuous influx of iron. Iron-pretreated cells were pulsed with [(35)S]Met for 60 min or with (59)Fe overnight and harvested up to 30 h thereafter, during which they were/were not cultured with ferric ammonium citrate (FAC; 180 microm). Radioactivity in ferritin/ferritin subunits of cell heat supernatants was determined by autoradiography of rockets obtained by immunoelectrophoresis or after precipitation with ferritin antibody and SDS-PAGE. Both methods gave similar results. During the +FAC chase, the concentration of ferritin in the cells increased linearly with time. Without FAC, the half-life of (35)S-ferritin was 19-20 h; with FAC there was no turnover. Without FAC, the iron in ferritin had an apparent half-life of 20 h; in the presence of FAC there was no loss of (59)Fe. Without FAC, concentrations of ferritin iron and protein also decreased in parallel. We conclude that a continuous influx of excess iron can completely inhibit the degradation of ferritin protein and that the iron and protein portions of ferritin molecules may be coordinately degraded.
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PMID:Iron prevents ferritin turnover in hepatic cells. 1160 70

Cubic F432 crystals of recombinant mouse L-chain apoferritin were obtained by the hanging-drop technique with ammonium sulfate and cadmium sulfate as precipitants. The structure was refined to 2.1 and 1.6 A resolution from data obtained at room temperature and under cryogenic conditions, respectively. The structure of an eight-amino-acid loop insertion in the mouse sequence is found to be highly disordered both at room temperature and at low temperature.
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PMID:Structure of mouse L-chain ferritin at 1.6 A resolution. 1167 11

Iron incorporation by bovine spleen apoferritin either with ferrous ammonium sulfate in different buffers or with ferrous ammonium sulfate and phosphate was studied. Iron uptake and iron autoxidation were recorded spectrophotomerically. The buffers [4-(2-hydroxyethyl)-1-piperazinyl]ethanesulphonic acid (Hepes) and tris(hydroxymethyl)aminoethane (Tris) exhibited pH-dependent iron autoxidation, with Tris showing less iron autoxidation than Hepes. An Eadie-Scatchard plot (v/[s] versus v) of the iron uptake rate in Hepes was a curved rather than a straight line, suggesting that there are two iron uptake pathways. On the other hand, the Eadie-Scatchard plots of Tris and of Hepes after the addition of phosphate showed a straight line. Phosphate accelerated the iron uptake rate. The iron loading kinetics of apoferritin in Hepes was dependent on apoferritin concentration. The Km value obtained from iron uptake kinetics was 4.5 microM, corresponding to the physiological iron concentration. These results demonstrate that iron loading of apoferritin was accomplished at physiological iron concentrations, which is essential for iron uptake, via two uptake pathways of dependent on iron concentration.
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PMID:Two pathways of iron uptake in bovine spleen apoferritin dependent on iron concentration. 1186 23

From the liver of fish Dasyatis akajei, ferritin has been isolated by thermal denaturation and ammonium sulfate fractionation and then further purified by anion exchange chromatography and gel exclusion chromatography. The molecular weight of the liver ferritin of D. akajei (DALF) was measured to be 400 kDa by PAGE. Moreover, SDS-PAGE experimentation indicates that protein shell of DALF consists of the H and L subunits with molecular weight of 18 and 13 kDa, respectively. Using isoelectric focusing with pH ranging from 5.0 to 6.0, the ferritin purified by the PAGE exhibited three bands with different pI values in the gel slab. Diameters of the protein shell and iron core were also investigated by transmission electron microscope and determined to be 10-12 nm and 5-8 nm, respectively. A kinetic study of DALF reveals that the rate of self-regulation of the protein shell rather than the complex surface of the iron core plays an important role in forming a process for iron release with mixed orders.
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PMID:Purification, electrophoretic behavior, and kinetics of iron release of liver ferritin of Dasyatis akajei. 1273 99

To provide necessary information for further understanding of molecular mechanism of hypoxia acclimatization, the differentially expressed genes of HepG2 cells exposed to normoxia, acute hypoxia-treated cells which were exposed to 1% oxygen for 48 h, and hypoxia-acclimatized HepG2 cells which were cultured for 6 circles of alternate low oxygen (1% oxygen for 24 h) and normal oxygen (21% oxygen for 24 h), were identified respectively by combining the suppression subtractive hybridization (SSH) and cDNA microarray. Thirty-seven genes were expressed differentially in cells exposed to 1% oxygen for 48 h compared with those in cells exposed to normoxia. The expression of all these 37 genes was down-regulated, including the genes participating in cell cycle, cell response to stimulus, and cell signal transduction, and cell cytoskeleton formation, the genes associated with transcription and cell metabolism, 4 expressed sequence tags (ESTs), and 12 genes of which the functions are not known. There is a novel gene sequence, which has not been found in existing databases. There were only 6 genes differentially expressed in the hypoxia-acclimatized cells compared with cells exposed to normoxia, including two mitochondrion genes, metalloprotease-1 gene, ferritin gene, thymosin beta-4 and TPT1 genes. The expressions of mitochondrion ND4, ferritin, thymosin beta-4 and TPT1 were up-regulated, while the expressions of mitochondrion ND1 gene and metalloproease-1 gene were down-regulated. Cell tolerance to hypoxia increased after the cells were hypoxia-acclimatized. The different gene expression patterns of the acute hypoxia-treated cells and the hypoxia-acclimatized cells may be related to the increased tolerance of the cells to hypoxia.
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PMID:[Identification of differentially expressed genes of acute hypoxia-treated HepG2 cells and hypoxia-acclimatized HepG2 cells]. 1281 1

The iron storage protein, apoferritin, has a cavity in which iron is oxidized and stored as a hydrated oxide core. The size of the core is about 7 nm in diameter and is regulated by the cavity size. The cavity can be utilized as a nanoreactor to grow inorganic crystals. We incubated apoferritin in nickel or chromium salt solutions to fabricate hydroxide nanoparticles in the cavity. By using a solution containing dissolved carbon dioxide and by precisely controlling the pH, we succeeded in fabricating nickel and chromium cores. During the hydroxylation process of nickel ions a large portion of the apoferritin precipitated through bulk precipitation of nickel hydroxide. Bulk precipitation was suppressed by adding ammonium ions. However, even in the presence of ammonium ions the core did not form using a degassed solution. We concluded that carbonate ions were indispensable for core formation and that the ammonium ions prevented precipitation in the bulk solution. The optimized condition for nickel core formation was 0.3 mg/mL horse spleen apoferritin and 5 mM ammonium nickel sulfate in water containing dissolved carbon dioxide. The pH was maintained at 8.65 using two buffer solutions: 150 mM HEPES (pH 7.5) and 195 mM CAPSO (pH 9.5) with 20 mM ammonium at 23 degrees C. The pH had not changed after 48 h. After 24 h of incubation, all apoferritins remained in the supernatant and all of them had cores. Recombinant L-ferritin showed less precipitation even above a pH of 8.65. A chromium core was formed under the following conditions: 0.1 mg/mL apoferritin, 1 mM ammonium chromium sulfate, 100 mM HEPES (pH 7.5) with a solution containing dissolved carbon dioxide. About 80% of the supernatant apoferritin (0.07 mg/mL) formed a core. In nickel and chromium core formation, carbonate ions would play an important role in accelerating the hydroxylation in the apoferritin cavity compared to the bulk solution outside.
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PMID:Fabrication of nickel and chromium nanoparticles using the protein cage of apoferritin. 1296 75

Aminoacetone (AA) is a threonine and glycine metabolite overproduced and recently implicated as a contributing source of methylglyoxal (MG) in conditions of ketosis. Oxidation of AA to MG, NH4+, and H2O2 has been reported to be catalyzed by a copper-dependent semicarbazide sensitive amine oxidase (SSAO) as well as by copper- and iron ion-catalyzed reactions with oxygen. We previously demonstrated that AA-generated O2*-. and enoyl radical (AA*) induce dose-dependent Fe(II) release from horse spleen ferritin (HoSF); no reaction occurs under nitrogen. In the present study we further explored the mechanism of iron release and the effect of AA on the ferritin apoprotein. Iron chelators such as EDTA, ATP and citrate, and phosphate accelerated AA-promoted iron release from HoSF, which was faster in horse spleen isoferritins containing larger amounts of phosphate in the core. Incubation of apoferritin with AA (2.5-50 mM, after 6 h) changes the apoprotein electrophoretic behavior, suggesting a structural modification of the apoprotein by AA-generated ROS. Superoxide dismutase (SOD) was able to partially protect apoferritin from structural modification whereas catalase, ethanol, and mannitol were ineffective in protection. Incubation of apoferritin with AA (1-10 mM) produced a dose-dependent decrease in tryptophan fluorescence (13-30%, after 5 h), and a partial depletion of protein thiols (29% after 24 h). The AA promoted damage to apoferritin produced a 40% decrease in apoprotein ferroxidase activity and an 80% decrease in its iron uptake ability. The current findings of changes in ferritin and apoferritin may contribute to intracellular iron-induced oxidative stress during AA formation in ketosis and diabetes mellitus.
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PMID:Aminoacetone induces loss of ferritin ferroxidase and iron uptake activities. 1470 1


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