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

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

Polycations induce loss of fixed anionic sites in the glomerular capillary wall and epithelial changes similar to those reported in proteinuric conditions. To investigate whether such alterations are accompanied by an increase in glomerular permeability, the distribution of anionic ferritin was studied in kidneys perfused with a polycation (protamine sulfate). Cortical biopsies were examined by light and electron microscopy. Glomerular anionic sites were studied by the colloidal iron reaction. In kidneys perfused with protamine, whether or not pretreated with heparin, there was a marked decrease in glomerular polyanion, a flattening and loss of foot processes, and a significant increase in number of ferritin molecules beyond the inner aspect of the glomerular basement membrane, relative to controls. When protamine-treated kidneys were reperfused with heparin, there was restoration of glomerular polyanion, nearly complete reversion of epithelial changes, formation of protamine-heparin complexes in the capillary wall, and a ferritin distribution comparable to that of controls. These results provide additional evidence evidence of the restrictive role of the glomerular polyanion with respect to the filtration of anionic proteins.
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PMID:Glomerular permeability: transfer of native ferritin in glomeruli with decreased anionic sites. 73 59

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

Homogenization of guinea pig liver in isotonic sucrose solution followed by the separation of the subcellular fractions by differential centrifugation releases the liver L-asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1) activity into the supernatant fraction. Electron micrographs of the liver L-asparaginase-antibody complexes, precipitated from the clear supernatant phase by addition of L-asparaginase-specific antiserum, show membrane-liek structures and some amorphous material. The attachment of L-asparaginase to the membrane-like structures is indicated by the ferritin-labeled antibody technique. The immunoprecipitates possess low activities of 5'-nucleotidase, alkaline phosphodiesterase I, NADPH cytochrome c reductase, glucose-6-phosphatase, and acid phosphatase. This observation suggests that L-asparaginase found in the liver supernatant fraction is associated with cytomembrane components. Analysis of guinae pig serum L-asparaginase-antibody complexes is polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate gives three distinct protein bands. These bands correspond to heavy and light chains of rabbit immunoglobulins and the L-asparaginase subunits. Analysis of the liver L-asparaginase-antibody complexes by the above procedure shows similar but more diffuse protein bands.
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PMID:Evidence for the association of L-asparaginase with cytomembrane components in the guinea pig liver soluble fraction. 81 93

The detailed reversible binding isotherms of sodium dodecyl sulfate (NaDodSO4) with 13 different initially native proteins are reported; the data were obtained at 20 degrees C and pH 7.1, ionic strength 0.033, with amounts bound with some proteins up to 1.1 g per g of protein. Although the isotherms of some of the proteins do not vary widely, extreme variations between certain classes are found. Thus, for example, hemoglobin and myoglobin both have high affinities and high binding capacities, while gamma-globulin, apoferritin, and transferrin have low initial affinities, and change drastically at higher concentrations. The protein-NaDodSO4 complexes solubilize the water-insoluble dye dimethylaminoazobenzene (DMAB) as effectively as micelles of pure NaDodSO4 when only small amounts (0.2 to 0.5 g/g of NaDodSO4) are bound. In most cases this effectiveness falls progressively as larger amounts are bound, and may even cease altogether at limits characteristic of the individual protein. With some of the latter, a second region of renewed solubilization occurs when substantially higher amounts of NaDodSO4 are present. In all cases, solubilization by ordinary micelles in normal amount occurs when the free NaDodSO4 concentration exceeds the critical micelle concentration, but the binding of NPADodSO4 to the protein also increases, in competition with formation of micelles. With some, but not all proteins the NaDodSO4 bound at concentrations above the cmc also solubilizes DMAB. In such cases the solubilizations by the protein-NaDodSO4 complexes and by the simple micelles are additive. The significance of the differences in binding and solubilizing encountered among these proteins is discussed in terms of surface structure, cooperativity of binding, and protein composition. No certain correlations with content of most amino acids, subunit structure, solubility, and hydrophobicity have been found, but there is a weak inverse dependence of solubilizing effectiveness on molecular size and indications of a strong dependence on content of cationic groups.
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PMID:Differences in the solubilizing effectiveness of the sodium dodecyl sulfate complexes of various proteins. 83 11

Fifty piglets from birth to 14 days of age were used to investigate iron binding substances of neonatal intestinal mucosa, and to evaluate the effects of these substances in neonatal iron absorption. 59Fe-labeled ferric citrate with a molecular weight of 1,500 was injected directly into the ligated duodenum. Approximately 65% of radioiron in the whole homogenate of scraped intestinal mucosa was precipitate by centrifugation for 30 minutes at 10,000 X g. Over 70% of the radioiron of the supernatant applied to Sephadex G-200 column was eluted and separated into three radioiron fractions. These iron binding substances were identified as ferritin, transferrin and a low molecular weight form by elution characteristics on chromatography and by immunological technique. Although ferritin radioactivity was the major fraction of peak 1 (73%), transferrin activity was only 54% of the whole radioiron of peak 2. The sodium dodecyl sulfate (SDS) extract of saline insoluble particles from the mucosa applied to Sepharose 4B column eluted as a single peak near the point corresponded with the ferritin peak. Although the ferritin peak contained a higher percentage of the 59Fe than the transferrin peak at birth, the percentage of ferritin decreased and percentage of transferrin increased with age. A SDS soluble iron binding substance was found in the insoluble particles of mucosa of newborn as well as nursing piglets. Since SDS, as well as saline soluble, iron binding proteins were detected in the newborn intestinal mucosa, neonatal cell membrane and cytoplasma may have an active iron transfer system. Thus, it seems likely that neonatal mucosal cell has two active iron transport mechanisms: endocytosis and transport across the plasma membrane.
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PMID:Iron binding substances in the intestinal mucosa of neonatal piglets. 84 85

A Triton X-100 solubilized macromolecular complex of transferrin and a membrane constituent can be isolated by gel chromatography from rabbit reticulocytes previously incubated with 125I-labeled transferrin. The apparent molecular weight of this complex is close to that of ferritin, or about 445 000. On sodium dodecyl sulfate gel electrophoresis the complex displays two glycoprotein subunits, of molecular weights 176 000 and 95 000 in addition to transferrin. A transferrin-binding fraction with a molecular weight near 400 000, containing these subunits, can also be identified in membranes of nonincubated reticulocytes. The corresponding membrane fraction from mature erythrocytes, which have lost transferrin-binding activity, displays both protein subunits, but the 176 000 molecular weight component fails to give a PAS stain for carbohydrate. Treatment of reticulocytes with Pronase, which destroys the ability of the cells to form specific complexes with transferrin, degrades both components. We believe these results are consistent with the hypothesis that the primary transferrin receptor of the rabbit reticulocyte is a glycoprotein of molecular weight in the range 350 000-400 000, comprised of a combination of two subunits with molecular weights 176 000 and 95 000, respectively. Transferrin-binding activity appears to depend on the carbohydrate moiety of the 176 000 subunit.
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PMID:Transferrin receptor of the rabbit reticulocyte. 84 17

Ferritin extracted from rat heart containes two species separable by gel electrophoresis. These were purified and examined for structural characteristics. As in gel electrophoresis, cardiac ferritin preparations yielded only two bands on isoelectric focusing in gels, with pI values of 4.6 and 4.8. After separation by preparative electrophoresis, the two species were found to have a different amino acid composition from each another and from liver ferritin. Similarly, peptide maps showed several components not found in liver ferritin. On dissociation and electrophoresis with sodium dodecyl sulfate, heart ferritins were found to contain subunits of the same sizes as in other rat ferritins but also some larger components. Since cardiac ferritins have apparent molecular weights greater than those of other ferritins, it is concluded they probably contain more subunits, and possibly some of larger size not present in ferritins of other tissues.
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PMID:Structural features of rat cardiac ferritins. 84 69

Twenty-four hours after the administration of Ga-67 citrate and Fe-59 citrate, rabbits were killed and their livers removed and homogenized. Labile proteins in the filtered liver homogenates were denatured; ferritin was then crystallized from the supernatants by cadmium sulfate. Sephadex G-200 gel filtration of the ferritin fractions was done to determine the distribution of molecular weights in the substances associated with Ga-67 and Fe-59. It was found that Ga-67 was incorporated into the crystallizable ferritin fraction of rabbit hepatocytes with approximately one-sixth the uptake of simultaneously administered Fe-59. Gel-filtration chromatography confirmed that both the Ga-67 and the Fe-59 of the crystallizable ferritin fraction were associated with substances of the appropriate molecular weight for ferritin.
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PMID:The incorporation of Ga-67 into the ferritin fraction of rabbit hepatocytes in vivo. 89 95


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