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

Chelating agents disrupted the superficial layers on Spirillum putridiconchylium and adsorption of cationized ferritin indicated that both upper and lower surfaces of superficial layer fragments, as well as the outer membrane surface, possessed areas which were negatively charged. Growth of the bacterium in 1% casamino acids (vitamin free) resulted in cells which were devoid of the superficial layers, and negative staining of these cells revealed in amorphous precipitate together with a vesicular outer membrane component extruding from their surfaces into the medium. Addition of either 1 mM Ca2+ or 1 mM Sr2+ to the growth medium produced the typical regularly structured cell surface, whereas addition of equal concentrations of Li+, Na+, K+, Mg2+, Ba2+, Mn2+, Fe3+, or three polyamines produced the structureless surface.
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PMID:Dependence of the superficial layers of Spirillum putridiconchylium on Ca2+ or Sr2+. 1 67

alpha2 H globulin, a glycoferroprotein, was first demonstrated in the sera of patients with malignant diseases. This protein was isolated from cancerous human liver, and compared with ferritin, a ferroprotein showing some identical properties (presence of iron, high molecular weight, common antigenic determinants). However, physicochemical differences were observed between these two proteins. The study of protein dissociation was performed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate after reduction by mercaptoethanol. A similar molecular weight of 19 000 is obtained for subunits of these two proteins. This value agrees well with the results obtained by other authors for ferritin.
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PMID:[Molecular weight of human alpha2-H-ferroglobulin subunits. Comparison with molecular weight of ferritin subunits]. 5 41

Experiments were carried out to locate carbamoyl phosphate synthetase (CPS) in rat liver by direct immunoferritin labeling. By using Epon sections treated with sodium methoxide, homogenates or mitochondrial and mitoplast fractions, carbamoyl phosphate synthetase was found homogeneously distributed in the mitochondrial matrix. Immunoferritin was detected with high resolution which permits the identification of individual molecules. Measurements were made of the number of ferritin particles per square micron of mitochondrial surface, providing a novel and independent assessment of the carbamoyl phosphate synthetase concentration.
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PMID:Immunoferritin location of carbamoyl phosphate synthetase in rat liver. 9 72

2 distinct macronuclear markers, ferritin and hemocyanin, may be used in a mixed anti-globulin labeling reaction to localize lymphocyte surface immunoglobulin (Ig) determinants by transmission electron microscopy. Soluble immune complexes of the marker molecules (antigen) are prepared by complexing with specific antiserum in 40 to 50 x antigen excess; uncomplexed Ig is removed by ultrascentrifugation and/or gel filtration chromatography. Immunoelectrophoresis, spectrophotometry and passive hemagglutination inhibition assay are used to determine the purity and amounts of antibody-antigen in the purified immune complexes. For immunoelectron microscopic labeling, the immune complex markers are coupled to lymphocyte surface Ig by an indirect anti-Ig or anti-allotype antibody linkage. Labelled Ig determinants at 0 degrees C or in the presence of sodium azide are visualized as small patches of marker molecules on the lymphocyte surface membrane. This EM labeling method results in much more consistent and generally higher percentages of surface Ig positive cells (60 to 70% of rabbit peripheral blood lymphocytes) than the percentages obtained using other methods, such as immunofluorescence or autoradiography. If the lymphocytes are warmed to 37 degrees C in the absence of azide the labeled surface Ig determinants undergo rapid endocytosis; endocytotic vesicles containing marker molecules are visible. This mixed anti-globulin immunoelectronmicroscopic labeling system may be used to localize a wide variety of antigens on different cell surfaces.
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PMID:Ultrastructural labeling of lymphocyte surface immunoglobulin: the preparation and use of soluble immune complexes as indirect immunoelectromicroscopic markers. 9 48

Ferritin has been purified from normal full-term human placentae and its antigenic and molecular characteristics compared with adult liver ferritin. Placental ferritin is composed predominantly of a single subunit type, co-migrating with a liver ferritin standard on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Comparison of dose-response curves in an immunoradiometric assay indicated some tissue-specific antigenicity for placental ferritin. This was supported by immunofluorescence studies on cryostat sections of human placentae by using antibodies to placental and spleen ferritin. Specific staining for placental ferritin was demonstrated within placental syncytiotrophoblast, particularly localized towards the microvillus plasma membrane. Ferritin has also been shown by electrophoretic and antigenic analysis to be present in protein fractions solubilized from isolated human syncytiotrophoblast microvillus plasma-membrane preparations, suggesting that ferritin may play an active role in the transfer of iron from maternal transferrin across the syncytiotrophoblast plasma membrane.
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PMID:Characterization and localization of human placental ferritin. 11 99

The distribution of (Na+ + K+) ATPase over the plasma membranes of distal convoluted tubules from canine kidney has been determined. This enzyme is responsible for the coupled active transport of Na+ and K+ across animal cell membranes. Ultrathin frozen sections were cut from fragments of renal cortex and specifically stained with antibodies, which recognize antigenic sites on the enzyme, and ferritin-conjugated goat antirabbit gamma-globulins. It is demonstrated that (Na+ + K+) ATPase is distributed uniformly and at high concentration over the plasma membranes which form the intercellular spaces of this epithelium. The enzyme is located on the luminal surface of the tubules as well but at a much lower concentration. These results, in combination with those of previous determinations of the cation fluxes across this epithelium, can be used to formulate a complete description of the cation movements through this tissue.
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PMID:Immunoferritin determination of the distribution of (Na+ + K+) ATPase over the plasma membranes of renal convoluted tubules. I. Distal segment. 12 57

The distribution of (Na+ + K+) ATPase over the plasma membranes of the proximal convoluted tubule from canine renal cortex has been determined. Ultrathin frozen sections of this tissue were stained with rabbit antibodies to this enzyme and ferritin-conjugated goat antirabbit gamma-globulin. It is demonstrated that high concentrations of this enzyme uniformly line the intercellular spaces of this epithelium. The consequences of this observation are discussed in terms of the low resistant tight junctions of these tubules and the isotonic fluid transport which they support. Furthermore, antibodies to (Na+ + K+) ATPase recognize an antigen on the luminal surfaces of the tubules within the brush border. It is proposed that the enzyme is present in this region of the plasma membrane as well, although at much lower concentration. To further substantiate this conclusion, a brush border fraction has been purified from rabbit kidney and been shown to contain significant (Na+ + K+) ATPase. These results contradict earlier conclusions about the location of (Na+ + K+) ATPase in this tissue.
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PMID:Immunoferritin determination of the distribution of (Na+ + K+) ATPase over the plasma membranes of renal convoluted tubules. II. Proximal segment. 12 58

Using precipitating antibodies to ACI rat liver ferritin and to sodium-dodecyl-sulfate-dissociated protein subunits of ACI rat liver ferritin, we have demonstrated the presence of ferritin-positive sites and subunit-positive sites in situ in several rat hepatoma cell lines by immunofluorescence. Hepatoma cells from three transplantable rat hepatomas (Reuber H-139, Reuber H-35, and Morris 5123) were explanted and propagated. Rabbit antibodies specific for either protein subunits of ferritin or ferritin were prepared by affinity chromatography or by dissociation of antibody-antigen complexes with 0.1 M acetic acid followed by differential ultracentrifugation. Explants of Reuber H-139, Reuber H-35, and Morris 5123 hepatoma cells, grown either in ordinary McCoy's 5a medium or in such medium enriched with iron (0.002% Fe), gave positive immunofluorescence for subunits as well as ferritin. Exposure of a clonal strain of Morris 5123 hepatoma cells to iron-enriched culture medium for varying lengths of time of up to 24 hours resulted in progressive increase in the quantity of ferritin-specific immunofluorescent cytoplasmic material, which was at first present diffusely, and later in clumps. By contrast, during the initial 24-hour period, subunit-specific immunofluorescence remained at relatively low intensity, with diffuse distribution through the cytoplasma. Our findings indicate a) the presence, in the cytoplasm, of the three kinds of hepatoma cells, of unassembled or only partly assembled subunits of fragments of subunits as well as of ferritin, and b) rapid assembly of the protein subunits into apoferritin and ferritin after administration of iron, so that the concentration of subunits in the cytoplasm was not significantly increased.
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PMID:Production of ferritin by rat hepatoma cells in vitro. Demonstration of protein subunits and ferritin by immunofluorescence. 16 99

An improved technique was developed for the unidirectional covalent binding of avidin to ferritin by reductive alkylation. The method is based on the oxidation of sugar moieties on avidin and subsequent coupling to amino groups of ferritin via Schiff's bases followed by reduction with sodium borohydride. The resultant conjugate was used as an ultrastructural marker for the localization of surface receptor sites on biotin-derivatized whole cells. Erythrocytes were treated chemically with sodium meta-periodate and biotin hydrazide in succession. The ferritin-avidin conjugates were used to label the biotin sites either before or after fixation of the cells. The density and distribution of ferritin avidin conjugates on cell surfaces were anlyzed on thin sections and compared with those of cationized ferritin, which were shown to bind anionic sites of the erythrocyte membrane. The extensions of this method for the visualization of other systems is discussed.
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PMID:Preparation of ferritin-avidin conjugates by reductive alkylation for use in electron microscopic cytochemistry. 18 77

Ferritin was dissociated into subunits by various denaturants and the subunits were examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Human, horse, rat, and rabbit ferritins all exhibited characteristic patterns of heterogeneity; components with molecular weights of about 19,000, 11,000, and 8,000 were invariably found in these preparations. This result contradicts earlier reports that ferritin consists of 24 identical subunits. These polypeptides were isolated, purified in the presence of low concentrations of detergent, and characterized. Evidence based on amino acid compositions, NH2-terminal analysis and investigation of detergent-induced breakdown products, indicated that the 19,000 molecular weight component is a composite of the 8,000 and 11,000 molecular weight chains. Circular dichroism studies showed that the 19,000 molecular weight polypeptide retained appreciable amounts of ordered secondary structure whereas the two lower molecular weight peptides were unfolded to a much greater extent. If the 8,000 and 11,000 molecular weight polypeptides were recombined in equimolar amounts and the denaturant was completely removed, a substance with electrophoretic mobility and morphological appearance of native apoferritin was obtained.
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PMID:Characterization of the different polypeptide components and analysis of subunit assembly in ferritin. 23 40


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