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

Chromium(VI) reduction was studied in a system composed of reduced nicotinamide adenine dinucleotide phosphate-cytochrome P450 oxidoreductase (NADPH-P450 reductase) and different iron chelators and iron sources. In an aerobic phosphate buffer containing iron(II), chromium(VI) was not reduced by the Fe2+ probably because of spontaneous autoxidation of Fe2+, but freshly made Fe2+, added directly to a CrVI-containing buffer, reduced CrVI. Under anaerobic conditions, iron(II) reduced chromium(VI) stoichiometrically. A systemic containing ethylenediaminetetraacetic acid (EDTA)-Fe3+, NADPH-P450 reductase and NADPH effectively reduced chromium(VI) anaerobically. Under aerobic conditions this reaction was inhibited by about 45%. Adenosine diphosphate (ADP)-Fe3+, which is a poor acceptor of electrons from NADPH-P450 reductase, reduced chromium(VI) only marginally, Mannitol slightly increased the aerobic CrVI reduction. Addition of superoxide dismutase and catalase, which both regenerate some O2, led to inhibition of CrVI reduction. Ferritin, NADPH-P450 reductase and the iron chelators, EDTA and citrate, reduced CrVI, indicating mobilization of Fe2+ from ferritin. Low levels of EDTA (55 mumol l-1) and citrate (100 mumol l-1) in contrast to high levels (5 mmol l-1) did not increase CrVI reduction in microsomes. Using 4-(2-hydroxyethyl)-1-piperazineethane sulfonic acid buffer instead of phosphate buffer, the CrVI-reducing activity was increased.
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PMID:The role of iron chelators and oxygen in the reduced nicotinamide adenine dinucleotide phosphate-cytochrome P450 oxidoreductase-dependent chromium(VI) reduction. 774 Dec 58

One mechanism by which Listeria monocytogenes is thought to obtain iron required for growth is through the extracellular reduction of a ferric iron source to the ferrous form. To better characterize this reductase activity we have developed a simple plate assay that allows detection of colonies of Listeria species able to reduce ferric iron. Cells are plated on an agar base medium containing a ferric iron source and ethylenediamine dihydroxyphenylacetic acid. Colonies are then overlain with soft agarose containing NADH, flavin mononucleotide, and Ferrozine, a chelator of ferrous iron. Colonies able to reduce the ferric iron source form a red-purple color as the ferrous iron is complexed with ferrozine. Using this qualitative assay we have shown that all species of Listeria are able to reduce ferric iron when presented as ferric ammonium citrate whereas most other species of Gram-positive and Gram-negative bacteria are not. Only Clostridium perfringens was able to reduce ferric iron to the same extent as Listeria. Listeria monocytogenes was further shown to be capable of reducing various ferric iron salts as well as iron bound to ferritin, transferrin, and 2,3-dihydroxybenzoic acid in the agar plate assay. The utility of this assay was demonstrated by using it to screen a bank of Tn916-derived mutants of L. monocytogenes for clones unable to reduce ferric iron. Four such mutants were identified and all were shown to have greatly decreased ferric reductase activity.
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PMID:Reduction of ferric iron by Listeria monocytogenes and other species of Listeria. 833 Feb 59

A novel extracellular mycobacterial enzyme was identified in the ruminant pathogen Mycobacterium paratuberculosis. The enzyme was capable of mobilizing iron from different sources such as ferric ammonium citrate, ferritin, and transferrin by reduction of the metal. The purified reductase had a calculated Mr of 17,000, was sensitive to proteinase K treatment, and had an isoelectric point of pH 9. Analysis of the amino acid composition revealed glycine, serine, asparagine (or aspartic acid), and glutamine (or glutamic acid) as the most frequently occurring residues. Enzymatic activity was highest at 37 degrees C and between pH 5 and 10. The calculated Km and Vmax for ferric ammonium citrate were 0.213 mM and 0.345 mM min(-1) mg(-1), respectively. Using a specific antireductase antibody in immunoelectron microscopy, we were able to detect the enzyme associated with intracellular mycobacteria in naturally M. paratuberculosis-infected bovine tissue. We prepose that the reductase of M. paratuberculosis represents an alternative strategy of mycobacteria to mobilize ferric iron and discuss its potential role in bacterial evasion of intracellular defense mechanisms.
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PMID:Identification and characterization of a novel extracellular ferric reductase from Mycobacterium paratuberculosis. 945 31

Rat liver DT-diaphorase (EC 1.6.99.2) catalyzed reductive N-denitration of tetryl (2,4,6-tri-nitrophenyl-N-methylnitramine) and 2,4-dinitrophenyl-N-methylnitramine, oxidizing the excess of NADPH. The reactions were accompanied by oxygen consumption and superoxide dismutase-sensitive reduction of added cytochrome c and reductive release of Fe2+ from ferritin. Quantitatively, the reactions of DT-diaphorase proceeded like single-electron reductive N-denitration of tetryl by ferredoxin:NADP+ reductase (EC 1.18.1.2) (Shah, M.M. and Spain, J.C. (1996) Biochem. Biophys. Res. Commun. 220, 563-568), which was additionally checked up in this work. Thus, although reductive N-denitration of nitrophenyl-N-nitramines is a net two-electron (hydride) transfer process, DT-diaphorase catalyzed the reaction in a single-electron way. These data point out the possibility of single-electron transfer steps during obligatory two-electron (hydride) reduction of quinones and nitroaromatics by DT-diaphorase.
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PMID:DT-diaphorase catalyzes N-denitration and redox cycling of tetryl. 978 67

Nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP) modulate iron regulatory protein (IRP) activity and may, therefore, affect iron uptake through transferrin receptor expression. However, iron also enters the cell as nontransferrin-bound iron (NTBI), and the aim of this study was to evaluate the effects of NO donors on NTBI transport in HepG2 cells, a model of liver physiology. Incubation with SNP and SNAP led to a time- and concentration-dependent reduction in Fe3+ and Fe2+ uptake, thus indicating an effect on the transporter rather than on the reductase. In terms of Fe2+ uptake, no variations in the Michaelis-Menten constant (Km) and a reduction in maximum uptake (Vmax) (50, 33, and 16.6 fmol/microgram protein/min in control, SNP-, and SNAP-treated cells, respectively) were detected, which suggested a decrease in the number of putative NTBI transport protein(s). Gel shift assays showed that IRP activity was reduced by SNP and slightly increased by SNAP. Northern blot analysis of transferrin receptor messenger RNA (mRNA) levels showed variations similar to those observed for IRPs, but both NO donors increased L-ferritin mRNA levels and had no effect on the stimulator of Fe transport (SFT) mRNA. In conclusion, NO donors significantly reduce NTBI transport in HepG2 cells, an effect that seems to be IRP and SFT independent. Moreover, the reduction in NTBI uptake after NO treatment suggests that this form of iron may play a minor role in the increased hepatic iron stores observed in inflammation or that other liver cells are more involved in this pathological condition.
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PMID:Nitric oxide reduces nontransferrin-bound iron transport in HepG2 cells. 991 23

Intracellular iron concentration requires tight control and is regulated both at the uptake and storage levels. Our knowledge of the role that the iron-storage protein ferritins play in plants is still very limited. Overexpression of this protein, either in the cytoplasm or the plastids of transgenic tobacco, was obtained by placing soybean ferritin cDNA cassettes under the control of the CAMV 35S promoter. The protein accumulated in 4- and 6-day-old seedlings and in leaves of 3-week-old plants but not in dry seeds or in 2-day-old seedlings, which is consistent with previous reports describing a post-transcriptional control of ferritin amounts during the germination process. Overaccumulated ferritin in leaves was correctly assembled as 24-mers. Transformants were more resistant to methylviologen toxicity, indicating that the transgenic ferritins were functional in vivo. Ferritin overaccumulation in transgenic tobacco leaves leads to an illegitimate iron sequestration. As a consequence, these transgenic plants behave as iron deficient and activate iron transport systems as revealed by an increase in root ferric reductase activity and in leaf iron content.
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PMID:Iron homeostasis alteration in transgenic tobacco overexpressing ferritin. 1006 70

Chlorella protothecoides cultures grown in a nitrogen-free bleaching medium (BM-N) in the dark rapidly degraded chlorophyll (Chl) to red catabolites. This degreening process was investigated under different growth conditions. Supply of nitrogen to the culture medium (BM+N) inhibited bleaching and the synthesis of catabolites as did the addition to BM-N of cycloheximide or a chelator, 2,2'-bipyridyl. In contrast, chloramphenicol or the protease inhibitor E64 had no effect. During bleaching, Chl breakdown was accompanied by the degradation of cellular proteins such as light-harvesting complex II, cytochrome f and protochlorophyllide oxido-reductase. During growth in BM-N, protease activity increased and proteins immunologically detectable with an antibody against a senescence-enhanced cysteine protease accumulated. cDNAs from BM-N and BM+N cells were used for differential and subtractive screening to isolate cDNAs representing genes with degreening-enhanced expression (dee) in C. protothecoides. Several different dees were identified with different patterns of expression during Chlorella growth but which were all expressed at higher levels during bleaching. Among these, dee4 was most abundant and its expression was exclusive in BM-N cultures. Analysis of the dee sequences showed that they encode different proteins including a novel amino acid carrier (dee4), ferritin, ATP-dependent citrate lyase, a Ca2+-binding protein, MO25, ubiquinone-cytochrome c-reductase and several new proteins.
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PMID:Chlorophyll breakdown in Chlorella protothecoides: characterization of degreening and cloning of degreening-related genes. 1079 14

The Staphylococcus aureus genome encodes three ferric uptake regulator (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of PerR, we inactivated the gene by allelic replacement using a kanamycin cassette, creating strain MJH001 (perR). PerR was found to control transcription of the genes encoding the oxidative stress resistance proteins catalase (KatA), alkyl hydroperoxide reductase (AhpCF), bacterioferritin comigratory protein (Bcp), and thioredoxin reductase (TrxB). Furthermore, PerR regulates transcription of the genes encoding the iron storage proteins ferritin (Ftn) and the ferritin-like Dps homologue, MrgA. Transcription of perR was autoregulated, and PerR repressed transcription of the iron homeostasis regulator Fur, which is a positive regulator of catalase expression. PerR functions as a manganese-dependent, transcriptional repressor of the identified regulon. Elevated iron concentrations produced induction of the PerR regulon. PerR may act as a peroxide sensor, since addition of external hydrogen peroxide to 8325-4 (wild type) resulted in increased transcription of most of the PerR regulon, except for fur and perR itself. The PerR-regulated katA gene encodes the sole catalase of S. aureus, which is an important starvation survival determinant but is surprisingly not required for pathogenicity in a murine skin abscess model of infection. In contrast, PerR is not necessary for starvation survival but is required for full virulence (P < 0.005) in this model of infection. PerR of S. aureus may act as a redox sentinel protein during infection, analogous to the in vitro activities of OxyR and PerR of Escherichia coli and Bacillus subtilis, respectively. However, it differs in its response to the metal balance within the cell and has the added capability of regulating iron uptake and storage.
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PMID:PerR controls oxidative stress resistance and iron storage proteins and is required for virulence in Staphylococcus aureus. 1134 39

The dpr gene is an antioxidant gene which was isolated from the Streptococcus mutans chromosome by its ability to complement an alkyl hydroperoxide reductase-deficient mutant of Escherichia coli, and it was proven to play an indispensable role in oxygen tolerance in S. mutans. Here, we purified the 20-kDa dpr gene product, Dpr, from a crude extract of S. mutans as an iron-binding protein and found that Dpr formed a spherical oligomer about 9 nm in diameter. Molecular weight determinations of Dpr in solution by analytical ultracentrifugation and light-scattering analyses gave values of 223,000 to 292,000, consistent with a subunit composition of 11.5 to 15 subunits per molecule. The purified Dpr contained iron and zinc atoms and had an ability to incorporate up to 480 iron and 11.2 zinc atoms per molecule. Unlike E. coli Dps and two other members of the Dps family, Dpr was unable to bind DNA. One hundred nanomolar Dpr prevented by more than 90% the formation of hydroxyl radical generated by 10 microM iron(II) salt in vitro. The data shown in this study indicate that Dpr may act as a ferritin-like iron-binding protein in S. mutans and may allow this catalase- and heme-peroxidase-deficient bacterium to grow under air by limiting the iron-catalyzed Fenton reaction.
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PMID:An iron-binding protein, Dpr, from Streptococcus mutans prevents iron-dependent hydroxyl radical formation in vitro. 1200 33

Hereditary hemochromatosis is characterized by marked variation of expression of the defect: very few homozygotes with the C282Y/C282Y HFE genotype have full-blown clinical disease, a larger number show biochemical stigmata of iron overload, and some seem normal biochemically. The following candidate genes have been examined in detail to determine whether polymorphisms in them may be responsible for this variation: transferrin, transferrin receptor 1, transferrin receptor 2, ferritin-L, ferritin-H, IRP1, IRP2, HFE, beta(2) microglobulin, mobilferrin/calreticulin, ceruloplasmin, ferroportin, NRAMP1, NRAMP2 (DMT1), haptoglobin, heme oxygenase-1, heme oxygenase-2, hepcidin, USF2, ZIRTL, duodenal cytochrome b ferric reductase (DCYTB), TNFalpha, keratin 8, and keratin 18. The coding sequence, exon-intron junctions, and promoters of each of these genes was sequenced in DNA from 20 subjects: 5 HFE C282Y/C282Y with clinical disease, 5 HFE C282Y/C282Y with normal/low ferritin levels and no disease, 5 wt/wt with high ferritin and transferrin saturation, and 5 wt/wt normal controls. When coding or promoter polymorphisms were encountered, DNA from large numbers of ethnically defined subjects was examined for these polymorphisms and a relationship between their existence and abnormalities of iron homeostasis was sought. Only in the case of one transferrin mutation did we find a strong relationship between the polymorphism and iron deficiency anemia. The putative genes that affect the expression of HFE mutations remain elusive.
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PMID:Seeking candidate mutations that affect iron homeostasis. 1254 38


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