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)

The choriocapillaris is one example of a capillary bed lined by a fenestrated endothelium that is restrictive to exogenous tracers and endogenous plasma proteins. In this study we have examined the distribution of cell-surface monosaccharides utilizing biotinylated lectin-avidin ferritin cytochemistry. Receptors for wheat germ agglutinin were localized to the plasmalemma and diaphragms of some fenestrae, vesicles, and channels at the luminal endothelial front in amounts greater than seen for the other lectins employed. The absence of labeling following inhibition with N-acetylglucosamine and after tissue digestion with N-acetylhexosaminidase, but not after neuraminidase indicated that this lectin marked N-acetylglucosamine residues and not sialic acid. Wheat germ agglutinin receptors were not affected by pronase E or trypsin digestion, but were partially removed by proteinase K. The latter also removed many fenestral diaphragms. Wheat germ agglutinin receptors were cleaved with endoglycosidase D. The combined results indicate that the wheat germ agglutinin receptor is of the low-mannose type and part of a protein with hydrophobic properties. Receptors for concanavalin A (mannose) and Ricinus communis agglutinin (galactose) were also localized to the plasmalemma and endothelial diaphragms. The examination of sections at different tilt angles revealed that these lectins bound to the endothelium in a non-random distribution, encircling diaphragms of fenestrae and channels. Soybean agglutinin (N-acetylgalactosamine) marked endothelial structures sparsely. Following digestion with pronase E or trypsin, receptor sugars for the latter three lectins were completely removed, indicating their presence on protease susceptible glycoproteins. These findings demonstrate that the endothelium of the choriocapillaris bears carbohydrate moieties that are different than those described for permeable fenestrated endothelia.
 ...
PMID:The cell surface of a restrictive fenestrated endothelium. I. Distribution of lectin-receptor monosaccharides on the choriocapillaris. 394 19

The coding regions of the cDNAs for cytoplasmic soma ferritin and secreted yolk ferritin from the snail Lymnaea stagnalis were inserted into the prokaryotic expression vector pEMBLex2. The vector directed the synthesis in Escherichia coli of soma ferritin up to a concentration of 15% of soluble proteins. Soma ferritin was expressed as the multimeric protein (480 kDa). Its similarity with natural soma ferritin was confirmed by PAGE, immunostaining and electron microscopy. Yolk ferritin was expressed in the form of inclusion bodies. Attempts to refold and assemble the purified yolk ferritin subunit in vitro failed. The yolk ferritin coding sequence was therefore inserted into the expression vector pMAL-p2. At a growth temperature of the bacterial cells of 23 degrees C and at an isopropyl beta-D-thiogalactopyranoside concentration of 50 microM, about 5% of the induced MalE-yolk-ferritin fusion protein was secreted into the periplasmic space and could be purified by affinity chromatography on amylose; the rest occurred as insoluble cytoplasmic inclusion bodies. Soluble MalE-yolk-ferritin fusion protein was capable of assembly into ferritin-like particles. Fully assembled yolk apoferritin shells (610 kDa) were obtained by digestion of these particles with proteinase K (yield: 180 micrograms yolk ferritin/l bacterial culture). Recombinant yolk ferritin was capable of taking up iron in vitro. Yolk ferritin (610 kDa) and soma ferritin (480 kDa) were run to the pore limit of a non-denaturing 5-20% PAGE gradient gel. Under these conditions, yolk ferritin had a higher mobility than soma ferritin (480 kDa) and therefore the yolk ferritin may have a rather compact structure. A 41-amino-acid-residue stretch of the insertion, a distinctive feature of the yolk ferritin subunit, was deleted by site-directed mutagenesis. The MalE-yolk-ferritin variant thus obtained was readily degradable by proteinase K and could not be assembled into ferritin-like particles. Therefore residues in the deleted peptide must be important for the maintenance of the native structure.
 ...
PMID:Expression in Escherichia coli of a secreted invertebrate ferritin. 802 Apr 74

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.
 ...
PMID:Identification and characterization of a novel extracellular ferric reductase from Mycobacterium paratuberculosis. 945 31

Among the wall-less mycoplasmas only a few species have been identified with a capsule at their cell surface. Mycoplasma penetrans is a recently identified mycoplasma with unique morphology, isolated from HIV-infected patients. Using transmission electron microscopy, it was found that M. penetrans is surrounded by capsular material 11 nm (strain GTU-54-6A1) to 30 nm (strain HF-2) thick, which can be stained with ruthenium red and labelled with cationized ferritin. The polysaccharide composition of this capsule was indicated by its staining with periodic acid-thiocarbohydrazide silver proteinate and the abolition of ruthenium red staining of the cell surface by neuraminidase treatment. In addition, proteinase K treatment of the M. penetrans cells resulted in removal of the capsule, suggesting that polypeptides may contribute in anchoring it to the membrane or in its stability. Two different types of glycosylated material were detected in mycoplasma extracts by SDS-PAGE and periodic acid-Schiff staining. The first component was a high-molecular-mass material, which was heat- and proteinase-K-labile and which probably constitutes the capsular polymer. The other component was a low-molecular-mass glycolipid fraction, which was proteinase-K-, heat- and EDTA-resistant. The identification of a capsule at the M. penetrans cell surface is of particular interest for a mycoplasma which has been shown to adhere to various host cells and to penetrate into their intracellular compartments. The capsule may have significance in the pathogenesis of disease associated with infection by this organism.
 ...
PMID:Identification of two glycosylated components of Mycoplasma penetrans: a surface-exposed capsular polysaccharide and a glycolipid fraction. 961 99

Foodborne transmission of bovine spongiform encephalopathy (BSE) to humans as variant Creutzfeldt-Jakob disease (CJD) has affected over 100 individuals, and probably millions of others have been exposed to BSE-contaminated food substances. Despite these obvious public health concerns, surprisingly little is known about the mechanism by which PrP-scrapie (PrP(Sc)), the most reliable surrogate marker of infection in BSE-contaminated food, crosses the human intestinal epithelial cell barrier. Here we show that digestive enzyme (DE) treatment of sporadic CJD brain homogenate generates a C-terminal fragment similar to the proteinase K-resistant PrP(Sc) core of 27-30 kDa implicated in prion disease transmission and pathogenesis. Notably, DE treatment results in a PrP(Sc)-protein complex that is avidly transcytosed in vesicular structures across an in vitro model of the human intestinal epithelial cell barrier, regardless of the amount of endogenous PrP(C) expression. Unexpectedly, PrP(Sc) is cotransported with ferritin, a prominent component of the DE-treated PrP(Sc)-protein complex. The transport of PrP(Sc)-ferritin is sensitive to low temperature, brefeldin-A, and nocodazole treatment and is inhibited by excess free ferritin, implicating a receptor- or transporter-mediated pathway. Because ferritin shares considerable homology across species, these data suggest that PrP(Sc)-associated proteins, in particular ferritin, may facilitate PrP(Sc) uptake in the intestine from distant species, leading to a carrier state in humans.
 ...
PMID:Protease-resistant human prion protein and ferritin are cotransported across Caco-2 epithelial cells: implications for species barrier in prion uptake from the intestine. 1560 34

We characterized chicken erythrocyte and human platelet ferritin by biochemical studies and immunofluorescence. Erythrocyte ferritin was found to be a homopolymer of H-ferritin subunits, resistant to proteinase K digestion, heat stable, and contained iron. In mature chicken erythrocytes and human platelets, ferritin was localized at the marginal band, a ring-shaped peripheral microtubule bundle, and displayed properties of bona fide microtubule-associated proteins such as tau. Red blood cell ferritin association with the marginal band was confirmed by temperature-induced disassembly-reassembly of microtubules. During erythrocyte differentiation, ferritin co-localized with coalescing microtubules during marginal band formation. In addition, ferritin was found in the nuclei of mature erythrocytes, but was not detectable in those of bone marrow erythrocyte precursors. These results suggest that ferritin has a function in marginal band formation and possibly in protection of the marginal band from damaging effects of reactive oxygen species by sequestering iron in the mature erythrocyte. Moreover, our data suggest that ferritin and syncolin, a previously identified erythrocyte microtubule-associated protein, are identical. Nuclear ferritin might contribute to transcriptional silencing or, alternatively, constitute a ferritin reservoir.
 ...
PMID:Ferritin associates with marginal band microtubules. 1739 69