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

The regulation of ferritin synthesis by iron was examined in the reticulocytes of bullfrog tadpoles where the induction was 40- to 50-fold, increasing from 0.17 +/- 0.05% of total protein synthesis ([3H]leucine incorporation in cell suspension) to 7.4 +/- 1.6% following intraperitoneal injection of ferric ammonium citrate. No significant difference was observed between the levels of ferritin mRNA in control or iron-induced cells, determined by translation of isolated mRNA in a wheat germ system, demonstrating that ferritin induction by iron occurs by a post-transcriptional mechanism. Total protein synthesis in the wheat germ system was half-saturating at 10 micrograms of mRNA/ml whereas ferritin synthesis increased linearly up to 40 micrograms of mRNA/ml, demonstrating that the ferritin mRNA is translated with high efficiency relative to the total proteins synthesized. Studies with the cap analogue 7-methylguanosine-5'-monophosphate, suggest that cap binding is not directly involved in the high translational efficiency of the ferritin mRNA in the wheat germ system. The results indicate that iron-modulated changes in the availability of ferritin mRNA for translation, coupled with the high translational efficiency of the ferritin message, can account for the induction of ferritin synthesis by iron in embryonic erythroid cells.
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PMID:Translational control of ferritin synthesis by iron in embryonic reticulocytes of the bullfrog. 698 98

Particle Counting ImmunoAssay (PACIA) has been adapted to the determination of serum ferritin. Polystyrene particles (0.8 micrometers) were coated with anti-ferritin antibodies and the concentration of ferritin determined by the agglutinating activity of this protein. The agglutination was measured by the reduction of the number of non-agglutinated particles counted in an optical blood cell counter. Non-specific agglutination and inhibition of agglutination were prevented in 99% of clinical samples by the use of F(ab')2 fragments of the antiserum IgG to coat the particles and by using slightly dissociating conditions (pH 9.2, ammonium thiocyanate, EDTA). The system was automated with a sampling rate of 50/h and an incubation time of 25 min. The standard curve ranged from 1 to 100 micrograms/l; recoveries were between 93.6 to 100.2%; the correlation coefficients of PACIA with radioimmunoassays calculated respectively on 99 and 91 samples were 0.974 and 0.984; maximal within- and between assay CV were 11.2% and 7.7%.
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PMID:Particle counting immunoassay (PACIA) of ferritin. 707 28

RE ferritin synthesis in IHC was studied in M0s isolated from peripheral blood. Twelve phlebotomized hemochromatosis patients with normal body iron stores and 12 healthy control subjects were studied. M0s in culture were exposed to iron as either ferric ammonium citrate or iron dextran, and ferritin synthesis was determined by measurement of 3H-leucine incorporation after isolation of ferritin by a quantitative immunoadsorbent technique. Iron at concentrations of 150 and 300 microM induced de novo ferritin synthesis, increasing both 3H-leucine incorporation into ferritin and cellular ferritin content. However, no differences were observed between hemochromatosis and control M0s with respect to basal or iron-stimulated ferritin synthesis. The study has demonstrated that M0 ferritin synthesis in IHC does not differ from M0 ferritin synthesis in normal subjects and therefore suggests that the reported abnormalities in RE iron storage in IHC are not related to an inability of RE cells to synthesize ferritin.
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PMID:Ferritin synthesis in peripheral blood monocytes in idiopathic hemochromatosis. 708 66

Fibrils of Actinomyces viscosus WVU627 (numerical taxonomy cluster 1) were obtained by homogenization and purified by ultrafiltration, ammonium sulfate precipitations, gel filtration, and ion-exchange chromatography. Electron microscopy and resolution of a single band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis attested to the purity of the preparation. Purified fibrils were composed mainly of protein; small quantities of carbohydrate and phosphorus were detected. Immunoelectrophoresis revealed only a single precipitable antigen, which migrated slightly toward the anode, in reactions between purified fibrils and antiserum raised against either whole bacterial cells or the purified fibrils themselves. Immunoelectron microscopy with ferritin-conjugated antifibril antibody hemagglutination inhibition, and bacterial agglutination tests demonstrated that fibrils of Actinomyces viscosus cluster 1 strains shared some common antigens with clusters 2, 3, 4 and 6, but did not cross-react with typical Actinomyces naeslundii of cluster 5. Stability tests revealed that after heat or alkali treatment, the fibrils lost their antigenicity and disappeared from electron micrographs. They were affected less by sodium dodecyl sulfate, sonic, or acid treatments.
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PMID:Purification and characterization of surface fibrils from taxonomically typical Actinomyces viscosus WVU627. 727 34

The entry of fowl plague virus, and avian influenza A virus, into Madin-Darby canine kidney (MDCK) cells was examined both biochemically and morphologically. At low multiplicity and 0 degrees C, viruses bound to the cell surface but were not internalized. Binding was not greatly dependent on the pH of the medium and reached an equilibrium level in 60-90 min. Over 90% of the bound viruses were removed by neuraminidase but not by proteases. When cells with prebound virus were warmed to 37 degrees C, part of the virus became resistant to removal b neuraminidase, with a half-time of 10-15 min. After a brief lag period, degraded viral material was released into the medium. The neuraminidase-resistant virus was capable of infecting the cells and probably did so by an intracellular route, since ammonium chloride, a lysosomotropic agent, blocked both the infection and the degradation of viral protein. When the entry process was observed by electron microscopy, viruses were seen bound primarily to microvilli on the cell surface at 0 degrees C and, after warming at 37 degrees C, were endocytosed in coated pits, coated vesicles, and large smooth-surfaced vacuoles. Viruses were also present in smooth-surfaced invaginations and small smooth-surfaced vesicles at both temperatures. At physiological pH, no fusion of the virus with the plasma membrane was observed. When prebound virus was incubated at a pH of 5.5 or below for 1 min at 37 degrees C, fusion was, however, detected by ferritin immunolabeling. t low multiplicity, 90% of the prebound virus became neuraminidase-resistant and was presumably fused after only 30 s at low pH. These experiments suggest that fowl plague virus enters MDCK cells by endocytosis in coated pits and coated vesicles and is transported to the lysosome where the low pH initiates a fusion reaction ultimately resulting in the transfer of the genome into the cytoplasm. The entry pathway of fowl plague virus thus resembles tht earlier described for Semliki Forest virus.
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PMID:Infectious entry pathway of influenza virus in a canine kidney cell line. 732 11

We compared use of protein-A-containing Staphylococcus aureus bacteria with conventional ammonium sulfate precipitation and second-antibody methods of separating bound and free antigen in the radioimmunoassay of a hapten (digoxin) and protein (ferritin) in human sera. In each case, values obtained with the heat-killed, formalin-fixed bacteria correlated well with those found by established methods. No matrix effects were detected in either hapten or protein measurements. Because of the affinity of S. aureus for rabbit IgG, rabbit antisera could be used with a small number of bacteria to detect antigen in the presence of 50-fold excess human IgG. The availability of S. aureus and ease of handling make this reagent a rapid, economical alternative of general applicability in radioimmunoassay.
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PMID:Solid-phase radioimmunoassay with protein-A-bearing Staphylococcus aureus cells used to assay a protein (ferritin) and a hapten (digoxin). 735 69

It has been demonstrated that a cytochrome b-containing ferritin is present in Azotobacter vinelandii. After DEAE cellulose chromatography and purification fractional precipitation by 50% of the saturated ammonium sulfate of the extract prepared from A. vinelandii cells, a hexagonal crystalline preparation is obtained. The protein contains 4--6% of nonheme iron. The protein molecule is made up of an electron dense iron core with a diameter of 70A and a protein shell with a diameter of 120A. The Fe core can be removed from the shell by the treatment with chelating and reducing agents. Electron micrographs and absorption spectra reveal that the protein shells are very similar before and after the removal of the core. The electrophoretic mobility and immunological properties of the Fe-free protein against the antibody of ferritin are very similar to those of the protein before the removal of the iron. From the above characteristics, it can be inferred that the protein belongs to ferritin. The protein part contains protoheme as prosthetic group and so it belongs to cytochrome b. Hence, the protein prepared from A. vinelandii is a kind of cytochrome b-containing ferritins. The possible role of the ferritin in biological nitrogen fixation is discussed in this paper.
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PMID:Presence of a cytochrome b-containing ferritin in Azotobacter vinelandii. 744 25

The instability of oncogenic mRNA such as c-fos mRNA is controlled in cis by sequences present in both the coding and the 3' untranslated regions (3'UTR). The latter contains AU-rich elements (ARE) which, depending on the cellular context, mediate either their rapid degradation or inhibit their translation. These observations, along with the known increase of the life spans of many unstable mRNA promoted by inhibitors of protein synthesis, raise the possibility that both processes are linked. To investigate further the putative involvement of translation in both coding region and ARE-mediated rapid decay of c-fos mRNA, we designed an expression vector based on the use of the ferritin mRNA iron regulatory element (IRE). The latter structure links translation to intracellular iron concentration when inserted at the proper location within the 5'UTR. Rapid degradation of a beta-globin/c-fos 3'UTR construct was prevented by Desferrioxamine, an iron chelator, and facilitated by ferric ammonium citrate or hemin, while stability of other mRNAs not containing the IRE or the ARE were unchanged. The same conclusion was reached when the stability of a c-fos mRNA devoid of ARE was assessed in function of iron availability.
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PMID:c-fos mRNA instability determinants present within both the coding and the 3' non coding region link the degradation of this mRNA to its translation. 747 33

The present study aims at the role of ferritin in the regulation of syncytiotrophoblast free iron levels. The differentiated cytotrophoblast cell in culture is used as a model for this maternal-fetal interface. Cytotrophoblast cells isolated from term placentae are cultured in iron-poor (Medium 199), iron-depleted [desferrioxamine(DFO)] and iron-supplemented [diferric transferrin (hTF-2Fe), ferric ammonium citrate (FAC)] medium. Distribution and de novo synthesis of isoferritins is studied, together with the cellular iron concentration and the ferritin iron saturation. Compared to ferritin isolated from total placenta, ferritin obtained from villous tissue is enriched with acidic isoforms. This observation is in agreement with measured light (L) to heavy (H) subunit ratios < 1 of de novo synthesized ferritin in cultured cytotrophoblast cells. Neither iron-poor culture medium, nor hTf-2Fe supplemented medium affects the cellular iron or ferritin concentration. FAC increased the cellular ferritin iron saturation and (by synthesis) the acidic isoferritin concentrations. The results strongly suggest, that the term syncytiotrophoblast is able to balance transferrin-mediated iron uptake and iron release. In case of FAC supplementation, the syncytiotrophoblast is unable to keep intracellular iron low, and ferritin synthesis is stimulated. The predominance of acidic ferritins and the preferential synthesis of H subunits can be functionally explained by the established fact that iron incorporation in acidic ferritins is faster due to the presence of ferroxidase centres. Damage by free iron catalysed hydroxyl radical formation is therefore minimized.
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PMID:Ferritin in cultured human cytotrophoblasts: synthesis and subunit distribution. 756 1

Ferritin is an ubiquitous iron storage protein that plays a key role in determining the intracellular fate of iron. Therefore, ferritin synthesis is highly regulated by the iron status of the cell through post-transcriptional mechanisms that involve a specific high-affinity interaction between an iron-responsive element (IRE) in the 5' untranslated region of ferritin mRNA and a 98 kDa cytoplasmic protein, the iron-regulatory factor (IRF). The mechanisms that regulate the expression of the iron storage protein ferritin were investigated in erythroid (Friend erythroleukemia cell, FLC) and fibroblastic (L929 and B6) cell lines after exposure to various iron compounds. Both hemin (ferric protoporphyrin IX) and iron (as ferric ammonium citrate, FAC) were used as inducers of ferritin synthesis. Administration of hemin increases ferritin synthesis 8-12 fold both in erythroid and in non-erythroid cell lines, whereas FAC is a weak inducer of ferritin in FLC (only 5-fold). These results correlate with ferritin mRNA expression in FLC observed after hemin treatment compared to the effect exerted by FAC administration. This differential effect suggests that heme is the physiological compound able to stimulate ferritin synthesis in erythroid cell lines and that it plays an important physiological role in regulating gene expression in developing erythroid cells.
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PMID:Differential regulation of ferritin expression in Friend leukemia cells by iron compounds. 775 93


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