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

A complex containing the minor coat protein or adsorptionprotein (A protein) of bacteriophage fl has been solubilized from the fl virion, using the detergent deoxycholate. This complex was resolved from the fl DNA and from the fl major coat protein, or B protein, by gel filtration in the presence of deoxycholate. The A protein complex migrated as a single band on sodium dodecyl sulfate-urea-polyacrylamide gels corresponding to a molecular weight of 60 000. Analysis of the amino acid composition and amino terminal residues of this preparation indicates that the preparation contains a 20% contamination of additional protein species. Antibody against purified fd A protein is cross-reactive with deoxycholate-purified fl A protein and with fl phage. Electron microscopic observation of negatively stained complexes of fl phage with this anti-fd A protein antibody and ferritin conjugated goat anti-rabbit IgG antibody revealed phages with ferritin particles at their termini or complexes of two or more phages joined together at one end by ferritin, indicating that the complex of A protein molecules is located at one end of the filamentous fl virion.
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PMID:Adsorption protein of bacteriophage fl: solubilization in deoxycholate and localization in the fl virion. 32 64

The membrane receptor for Fc portions of IgG (FcR) was localized on the cell surface of humans lymphocytes by electron microscopy. The electron microscopic markers for FcR were soluble ferritin 7S anti-ferritin immune complexes prepared in forty times antigen excess than needed at equivalence. Fc receptors on the lymphocytes labelled at 0 degree in the presence of sodium azide were seen as discontinuous patches on the cell surface. In control experiments, no labelling was observed, which included lymphocytes treated with ferritin only or with F(ab')2 immune complexes as well as glutaraldehyde-fixed lymphocytes treated with 7S anti-ferritin immune complexes. The findings are discussed with relation to the widely accepted membrane fluidity model.
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PMID:Electron microscopy of Fc receptors on human lymphocytes. 43 49

Pure ferritin from male mouse liver produces a single band of monomers (RF = 0.199) with electrophoresis in polyacrylamide gels at pH 9.0. The five sub-bands within this monomeric band appear to represent charge isomers having the same molecular size. Ferritin from BH3 transplantable mouse hepatoma shows two overlapping bands of monomers (RFA = 0.208 and RFB = 0.240); further electrophoretic studies show that these bands represent two subpopulations of molecules differing both in charge and size. Sub-bands are not found in this hepatoma ferritin. The larger tumor ferritin reaches the same end migration position as all liver isoferritins on gradient gels, signifying a very similar or identical molecular size; however, the absence of sub-bands indicates that this hepatoma ferritin differs in charge from the homologous liver proteins. Liver and hepatoma ferritins both produce a single prominent subunit band corresponding to nominal molecular weights of 22 250 and 21 700, with polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and dithiothreitol. With electrophoresis on polyacrylamide gradient slabs containing sodium dodecyl sulfate and dithiothreitol, both liver and hepatoma ferritins now reveal two subunits bands situated at identical positions. The polypeptides of these two closely spaced bands have a nominal molecular weight difference of less than 1000. Neither the hepatoma nor the liver seems to produce the ferritins found in the other tissue. Nevertheless, all these ferritins are composed of the same two types of subunits, albeit in different relative amounts. Observed distinctions in the ferritins from these normal or neoplastic cells must reflect differences in assembly and processing, as well as in the regulated expression of the same ferritin genes.
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PMID:Mouse hepatoma and liver ferritins. Comparative structural studies. 46 27

Three prototype tridentate ligands (i.e., pyrazinecarboxaldehyde thiosemicarbazone, sodium pyrazinecarboxaldehyde dithiocarbazonate, and pyrazinecarboxaldehyde 2'-pyrazinylhydrazone) were prepared and evaluated for their relative abilities to remove iron from model systems designed to mimic particular aspects of chronic transfusional iron overload. These compounds were synthesized by condensation of pyrazinecarboxaldehyde with the appropriate substituted hydrazide. Iron-binding properties were determined, and the ability to remove iron from the proteins transferrin and ferritin was ascertained. An in vivo model system employing iron-loaded mice was used to demonstrate that all three compounds were effective at reducing tissue iron levels.
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PMID:Synthesis and evaluation of the thiosemicarbazone, dithiocarbazonate, and 2'-pyrazinylhydrazone of pyrazinecarboxaldehyde as agents for the treatment of iron overload. 53 78

Mammalian ferritins can be resolved into multiple components by isoelectric focusing, and each tissue contains a characteristic subset of isoferritins. Ferritin isolated from human liver was compared to acidic ferritin isolated from mid-gestational human placenta to define a structural basis for ferritin heterogeneity. Placenta ferritin contained several major bands with isoelectric points in the range of pI = 4.7-5.0 which were more acidic than the predominant isoferritins of human liver. Ferritin from each tissue was resistant to denaturation by 10 M urea and appeared to be identical by electron microscopy. Circular dichroism measurements revealed that placenta ferritin had substantially less ordered secondary structure than liver ferritin. Both types of ferritin contained only two subunits when analyzed by electrophoresis in sodium dodecyl sulfate gels, but isoelectric focusing of dissociated subunits in urea revealed 6-7 different components. In this system, placenta ferritin was enriched in the more acidic subunits and it completely lacked the most basic subunits noted in liver ferritin; placental ferritin had no unique components. Differences in isoelectric points among assembled ferritins from these two tissues appear to result from different proportions of these acidic and basic subunits.
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PMID:Characterization of ferritin from human placenta. Implications for analysis of tissue specificity and microheterogeneity of ferritins. 53 48

Syncytiotrophoblast microvillous plasma membrane (StMPM) preparations were obtained from human full-term placentae by previously published methods of cold saline extraction and phase centrifugation. Purity of these preparations was assessed by electron microscopy, enzyme analysis and hydroxyproline content. IgG, albumin, alkaline phosphatase, transferrin, ferritin and alpha 2-macroglobulin were consistently detected in the aqueous soluble fraction from sodium deoxycholate-solubilised StMPM preparations by antigenic or electrophoretic analysis, beta 2-Microglobulin was not detected in these preparations. Up to 21 discrete protein bands could be demonstrated by SDS--PAGE, and their molecular weights determined. Many of these components need to be further identified, including a glycoprotein of molecular weight 36 500 which was particularly prominent. The soluble fraction from StMPM preparations gave a single strong precipitin reaction in immunodiffusion against wheat germ agglutinin, but not against other lectins studied.
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PMID:Characterisation of the soluble fraction of human syncytiotrophoblast microvillous plasma membrane-associated proteins. 55 Nov 70

Anionic sites on the surface of Brucella canis were visualized in the electron microscope by staining with positively charged ferric oxide hydrosols in acetic acid (AI-reagent), or propanoic acid (PI-reagent), and with a polycationic ferritin derivative. With the AI-reagent, single or small aggregates of ferric oxide particles were bound to the cell surface of Br. canis, whereas, with the lipophilic PI-reagent, the microorganisms were heavily stained with focal aggregates of iron granules. The polycationic ferritin label was uniformly distributed over the entire cell surface of Br. canis. The ferritin label was not bound on the surface of the organisms after prior treatment with trichloroacetic acid or methanolic hydrochloric acid. Treatment with aqueous acetone, chloroform/methanol, diethyl ether, sodium deoxycholate, pronase, lysozyme, hyaluronidase, and sodium periodate neither influenced the morphology of the Brucella nor diminished their ionic binding sites. Our results indicate that the anionic sites on the cell surface of Br. canis may be carboxyl and phosphate groups of lipopolysaccharides.
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PMID:[Ultrastructural investigations on anionic surface sites of Brucella canis (author's transl)]. 60 17

A glycoprotein immunologically related to plasma cold-insoluble globulin (CIG) and fetal skin fibroblast fibronectin has been purified from second-trimester human amniotic fluid. This protein (amniotic fluid fibronectin) migrated more slowly than CIG on sodium dodecyl sulfate gel electrophoresis and showed greater polydispersity which could result, at least in part, from heterogeneity in glycosylation. Cloned human amniotic fluid epithelioid and fibroblastic cells synthesized and secreted a protein with similar properties into the culture medium. Fibronectin was shown to be associated with the pericellular and extracellular matrix of cultured amniotic fluid cells by immunofluorescence, lactoperoxidase-catalyzed iodination, and labeling with ferritin-conjugated antibodies. The kinetics of secretion of the protein were consistent with its role as a matrix protein. We anticipate that amniotic fluid fibronectin will prove to be the same protein which elsewhere in the body is incorporated into connective tissues and basement membranes. Amniotic fluid could, therefore, serve as a convenient source of in vivo synthesized fibronectin for biological and structural studies.
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PMID:Amniotic fluid fibronectin. Characterization and synthesis by cells in culture. 70 56

Subunit heterogeneity of human liver ferritin was investigated by two-dimensional electrophoretic methods. The protein which ordinarily remains assembled in 10 M urea solution was dissociated into subunits in acid-urea or sodium dodecyl sulfate solutions. In agreement with earlier studies, the subunits migrated as two bands in sodium dodecyl sulfate or acid-urea gel electrophoresis systems or in two-dimensional combinations of these systems. Isoelectric focusing methods, however, resolved four major subunit bands and three to five minor bands. Each of these components migrated as either a 22 000 or a 19 000 molecular weight component in sodium dodecyl sulfate gel electrophoresis in the second dimension. The multiple subunit model, which is contrary to currently accepted representations of ferritin structure, is compatible with certain inherent properties of the protein. Thus, ferritin was fractionated on the basis of iron content to show that the relative amounts of individual subunit types were directly dependent upon the iron composition of the protein. Iron-loaded molecules were deficient in the most basic subunit types, and apoferritin was enriched in these components. Aspects of microheterogeneity of assembled ferritin molecules were correlated to subunit heterogeneity, and discrete differences in subunit populations among purified isoferritin components were demonstrated.
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PMID:Correlations between subunit distribution, microheterogeneity, and iron content of human liver ferritin. 72 7

Horse spleen ferritin was fractionated into its constituent isoferritins by isoelectric focusing. Separated isoferritins were stable and showed no tendency to redistribute when re-examined by analytical gel focusing. All of the isoferritins were immunologically indistinguishable when tested with antibodies raised against unfractionated horse spleen ferritin. The separated isoferritins also had similar conformations as determined by circular dichroism. Iron distribution studies, however, revealed a wide disparity among the isoferritins. The most acidic components had the lowest iron content but the iron content did not vary systematically throughout the isoferritin spectrum. Natural apoferritin, isolated from the ferritin by density gradient centrifugation, focused exclusively as the acidic moieties, whereas apoferritin prepared by reduction of native ferritin exhibited a banding pattern similar to that of unfractionated ferritin. The subunit structure of the isoferritins was examined by gel electrophoresis in sodium dodecyl sulfate or acidic urea systems. Multiple subunit types were demonstrated by both methods. The relative proportion of these subunit types varied progressively through the isoferritin spectrum. This difference in subunit population appears to be the basis for much of the structural heterogeneity in the apoferritin shells.
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PMID:Differences in subunit composition and iron content of isoferritins. 80 92


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