Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We present here the physicochemical and biochemical properties of NBD-DFO, the 7-nitrobenz-2-oxa-1,3-diazole (NBD) derivative of the siderophore, desferrioxamine B (DFO) (Lytton et al., Mol. Pharmacol. 40, 584, 1991). Modification of DFO at its terminal amine renders it more lipophilic, imparts to it fluorescent properties, and is conservative of the high-affinity iron(III) binding capacity. NBD-DFO partitions readily from aqueous solution into n-octanol (Pcoeff = 5) and displays solvent-induced shifts in absorption and fluorescence spectra. The relative quantum yield of the probe's fluorescence increases over a 10-fold range with decreasing dielectric constant of the solvent. Fluorescence is quenched upon binding of iron(III) to the probe. We demonstrate here the application of NBD-DFO for the specific detection and monitoring of iron (III) in solutions and iron(III) mobilization from cells. Interactions between fluorescent siderophore and the ferriproteins ferritin and transferrin were monitored under physiological conditions. Iron removal from ferritin was evident by the demonstrable quenching of NBD-DFO fluorescence by scavenged iron(III). Quantitation of iron sequestered from cells by NBD-DFO or from other siderophore-iron(III) complexes was accomplished by dissociation of NBD-DFO-Fe complex by acidification and addition of excess ethylenediamin-etetraacetic acid. The sensitivity of the method and the iron specificity indicate its potential for monitoring chelatable iron under conditions of iron-mediated cell damage, iron overload, and diseases of iron imbalance such as malaria.
Anal Biochem 1992 Sep
PMID:Monitoring of iron(III) removal from biological sources using a fluorescent siderophore. 133 42

To explore the role of transcriptional factors in the genesis of the senescent phenotype, nuclear extracts from 4- and 30-month-old rat brains were analyzed for the presence of DNA-binding proteins able to interact with double-stranded oligonucleotides containing recognition sites for sequence-specific DNA-binding factors. Gel shift assays revealed that the DNA-binding efficiency of Sp1 is significantly reduced in aged animals compared to young ones, whereas CTF/NF1 and AP1 from young and old rat nuclear extracts bind their DNA targets with the same efficiency. The quantitative analysis of Sp1 by immunoblotting indicated that equivalent quantities and degrees of heterogeneity of Sp1 protein are present in both nuclear extracts, suggesting that the observed difference is not due to a different expression of this transcriptional factor. DNase I footprinting of the heavy chain ferritin gene promoter, which contains a Sp1 binding site, demonstrated that the nuclear extract from 30-month-old rat brain does not protect the region involved in the regulation of the H ferritin gene by Sp1. This results in a reduction of about 50% of the expression of the H ferritin mRNA in aged rat brains. Furthermore, the Sp1 binding sites present in the SV40 early promoter are not protected in a DNase I footprinting assay where a nuclear extract from 30-month-old rat brain was used as a source of DNA binding proteins. Liver nuclear extracts prepared from young and aged rats demonstrated that a decrease of Sp1 binding efficiency is similarly present in this tissue.
J Biol Chem 1992 Sep 05
PMID:Sp1 DNA binding efficiency is highly reduced in nuclear extracts from aged rat tissues. 138 57

The mRNA-binding protein, iron-regulatory factor (IRF) has a central role in iron metabolism. It coordinately increases transferrin-receptor mRNA stability and inhibits translation of ferritin and erythroid delta-aminolevulinate synthase mRNA by binding to specific mRNA structures, the iron-responsive elements (IRE). In gel-retardation assays, IRF had a broad tissue distribution, showing activity in cytosolic extracts from 12 mouse organs tested. In all these extracts, IRF could be further activated in vitro by 2-mercaptoethanol. In cultured mouse 3T6 fibroblasts, growth stimulation after low serum arrest increased IRF activity 10-fold, mainly through activation of existing inactive IRF. No change was observed during progression of 3T6 cells through the cell cycle. IRF activation by iron chelators has been postulated to result in the reduction of an intramolecular sulfhydryl group. In a search for redox conditions that regulate IRE binding of IRF, we studied several compounds in vitro or in vivo. Hemin, known to inactivate IRF in vivo, showed a similar, reversible effect in vitro, presumably by oxidizing IRF. However, this did not appear to be relevant for the mode of IRF regulation in vivo. Addition of protoporphyrin IX to intact cells induced IRF activity almost to the same extent as desferrioxamine. This effect was inhibited by iron salts, indicating that IRF is activated in vivo through depletion of a chelatable iron pool. In vitro activation by reductants other than 2-mercaptoethanol suggested some selectivity in their access to relevant sulfhydryl groups, but did not reveal which natural redox-sensitive compound might regulate IRF in vivo. However, in cultured cells, inactivation of free IRF by the sulfhydryl-specific oxidizing agent diamide was much more rapidly reversed than inactivation by iron salts. This indicates the direct involvement of a cellular reductant in setting IRF activity and suggests a rate-limiting IRF conformation that is reached only in the presence of iron, but not after diamide oxidation.
Eur J Biochem 1992 Sep 15
PMID:In vivo and in vitro modulation of the mRNA-binding activity of iron-regulatory factor. Tissue distribution and effects of cell proliferation, iron levels and redox state. 139 66

The mechanisms responsible for anaemia in leprosy were studied prior to the institution of therapy in 56 patients with active disease. Haematological indices, iron-related measurements, inflammatory markers and erythropoietin levels were assessed, with bone-marrow studies being performed on anaemic patients. Anaemia was more common in the patients with lepromatous leprosy (85.7%) than it was in the rest of the group (19%). The lepromatous group exhibited the disordered iron transport of the anaemia of chronic disorders in that they had a significantly lower mean serum iron level (P less than 0.05), and a mildly raised serum ferritin concentration. Anaemic lepromatous patients also showed a blunted erythropoietin response compared with controls with non-inflammatory anaemia. A subgroup of five anaemic subjects displayed apparently adequate transport of iron to the erythroid marrow (normal percentage transferrin saturations and appropriate sideroblast counts) and the blunted erythropoietin response appeared to be the dominant factor in the pathogenesis of their anaemia. Analysis of inflammatory markers revealed that while the erythrocyte sedimentation rate was very high in the lepromatous subjects, there was no concomitant rise in C-reactive protein concentration. This suggests the presence of a disordered cytokine-mediated acute phase response in the condition.
J Intern Med 1992 Sep
PMID:Anaemia, iron-related measurements and erythropoietin levels in untreated patients with active leprosy. 140 25

Although some protein folding theories sustain that the peptides (loops) that connect elements of more compact secondary structure may be important in the folding process, most of the data accumulated until now seems to contradict this notion. To approach this problem we have isolated and characterized a number of mutants in which the amino acid sequence of the peptide that connects helix D and helix E in the H-chain of human ferritin has been randomized. Our results indicate that, though no single loop residue is absolutely required for ferritin to attain the native conformation, most of the mutants that we have obtained by random regional mutagenesis, affect its folding/assembly process. This conclusion was reached utilizing a sensitive test that associates the color formed by a colony synthesizing a hybrid ferritin-beta-galactosidase protein to the ability of the ferritin domain to fold and assemble as the native protein. The characterization of the folding/assembly properties of our collection of mutants and the comparison of the mutant loop sequences, have allowed us to draw the following conclusions. Mutants that have positively charged residues at position 159, 160 or 161 fail to assemble into the native protein shell and form an insoluble aggregate. Interestingly some loop amino acid sequences cause the E-helix to reverse direction and to expose its COOH group, normally hidden inside the protein cavity, to the solvent. The propensity of a given ferritin mutant to fold into this "non-native" conformation can be attenuated by the introduction of Gly at position 159 and 164, as in the natural ferritin.
J Mol Biol 1992 Sep 20
PMID:Loop mutations can cause a substantial conformational change in the carboxy terminus of the ferritin protein. 140 67

The oral efficacy of the oral iron chelators 1,2-dimethyl-3-hydroxypyrid-4-one (CP20), 1,2-diethyl-3-hydroxypyrid-4-one (CP94) and desferrioxamine B (DFO) has been compared with intraperitoneal DFO in an experimental model of iron overload with similar biochemical and biophysical characteristics to those observed for human genetic haemochromatosis. The hepatic iron stores in the ferrocene-loaded rat were relatively stable and did not decrease at the end of the loading period. In contrast, the iron dextran rat model showed a rapid depletion of its iron stores 2 weeks after cessation of intraperitoneal injection. When CP20 and CP94 were administered to the ferrocene-loaded rat model in combination with an iron-free diet there were significant decreases in (i) total homogenate iron and (ii) hepatic ferritin iron when compared to the iron-loaded rat receiving the iron-free diet alone. Desferrioxamine, when administered by gavage, only showed chelation of ferritin iron, while intraperitoneal injection of desferrioxamine showed significant depletion of iron both in the total homogenate and ferritin. Subcellular fractionation of the hepatic organelle clearly showed that where there was depletion of homogenate iron there was a net decrease in the lysosomal fraction, while changes in ferritin iron were reflected by decreases in the cytosolic iron content. Although no assessment of net iron excretion was made, we suggest that the use of this animal model should ascertain the site of chelation by iron chelators.
Biochem Pharmacol 1992 Sep 25
PMID:Studies of in vivo iron mobilization by chelators in the ferrocene-loaded rat. 141 29

Routinely measuring iron status is necessary because not only are about 6% of Americans in significant negative iron balance, but about 1% have iron overload. Serum ferritin is in equilibrium with body iron stores, and is the only blood test that measures them. Barring inflammation, each one ng (0.0179 pmol) ferritin/ml of serum indicates approximately 10 mg (0.179 mmol) of body iron stores. Very early Stage I positive balance is best recognized by measuring saturation of iron binding capacity. Conversely, serum ferritin best recognizes early (Stage I and II) negative balance. Deviations from normal are: 1. Both stages of iron depletion (i.e. low stores, no dysfunction). Negative iron balance Stage I is reduced iron absorption producing moderately depleted iron stores. Stage II is severely depleted stores, without dysfunction. These stages include over half of all cases of negative iron balance. Treated with iron, they never progress to dysfunction, i.e. to disease. 2. Both stages of iron deficiency. Deficiency is inadequate iron for normal function, i.e. dysfunction, disease. Negative balance Stage III is dysfunction without anemia; Stage IV is with anemia. 3. Positive iron balance: Stage I is a multi-year period without dysfunction. Supplements of iron and/or vitamin C promote progression to dysfunction (disease). Iron removal prevents progression. Stage II is iron overload disease, encompassing years of insidiously progressive damage to tissues and organs from iron overload. Iron removal arrests progression.
Blood Rev 1992 Sep
PMID:Iron disorders can mimic anything, so always test for them. 142 81

Fluorescein isothiocyanate-cationized ferritin (FITC-CF) has hitherto been used mainly to identify structures in living cells by light microscopy, by virtue of its fluorescent properties. We show here that this conjugate can be used, after immediate fixation of the same cell sample and preparation of thin sections, to recognise the same structures, by virtue of the ferritin's electron opacity. The conjugate should thus have a new use as a single-application, dual-purpose probe, e.g. in endocytic studies. The procedure may have advantages over similar dual-purpose probes in not requiring staining or special treatment.
Histochemistry 1992 Sep
PMID:Amalgamation of two endocytic probe techniques: fluoresceinated cationized ferritin can show up, sequentially, selected structures, first in living cells and then by electron microscopy. 142 21

Increments in serum ferritin levels in adult onset Still's disease (AOSD) were reported to be higher than one could expect for a simple inflammatory state. When we analyzed the scores of 40 patients with various severe inflammatory diseases aside from AOSD, we recorded no serum ferritin values higher than 3,300 ng/ml (N less than 200 ng/ml). In 3 of 10 consecutive patients with AOSD, the ferritin levels were higher than 3,500. Among these 3 patients, one case had a ferritin value of 3,600 ng/ml and bone marrow aspirate showed a marked hyperplasia of mature appearing histiocytes, and the 2 other patients (serum ferritin levels of 65,000 ng/ml and 250,000 ng/ml) displayed the features of a hemophagocytic syndrome. In 2 patients with normal or mildly increased levels of ferritin, the bone marrow examination was normal. We suggest that very high serum ferritin levels encountered in AOSD reflect the presence of histiocytic hyperactivity that sometimes leads to a hemophagocytic syndrome.
J Rheumatol 1992 Sep
PMID:Hyperferritinemia in adult onset Still's disease and the hemophagocytic syndrome. 143 11

The measurement of erythrocyte zinc protoporphyrin (ZPP) with a hematofluorometer is known to be a simple and cost-effective method to screen iron deficiency and lead poisoning. We measured ZPP on blood samples from 201 children suffering from various diseases, which revealed that ZPP has better sensitivity and specificity for identifying iron deficiency than serum ferritin and percent transferrin saturation. ZPP levels in various anemias were also measured. ZPP rose markedly (> 200 mumol/mol heme) in untreated iron deficiency anemia and returned to normal in 3-4 months since the initiation of iron therapy. Moderate elevation of ZPP was observed in acute leukemia (at onset and during induction therapy), MDS, aplastic anemia and some other anemic conditions. These findings suggest that erythrocyte ferrochelatase may be unexpectedly affected in anemias even except lead poisoning.
Rinsho Ketsueki 1992 Sep
PMID:[The measurement of erythrocyte zinc protoporphyrin/heme ratio in various anemias in childhood]. 143 41


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>