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

Mouse liver ferritin is composed almost exclusively of polypeptide chains similar in molecular mass (22 kDa) to that characteristic of the major chain (H) found in heart ferritin isolated from human, horse or rat. In these species the predominant polypeptide of liver (L) is smaller (about 20 kDa). Here we show that mouse liver and horse spleen ferritins and apoferritins exhibit extensive structural homology as judged by the similarity in the diffraction patterns of their crystals grown from cadmium sulphate solutions. Implications of this finding are discussed.
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PMID:Structural homology between mouse liver and horse spleen ferritins. 397 4

Antibodies against a lysosomal membrane antigen (A-Ly-M) have recently been obtained and characterized (Reggio, H., D. Bainton, E. Harms, E. Coudrier, and D. Louvard, 1984, J. Cell Biol., 99:1511-1526). They recognize a 100,000-mol-wt antigen immunologically related to a purified [H+,K+]ATPase from pig gastric mucosa. In the present study, we have localized this antigen during adsorptive endocytosis in rat prolactin cells in culture using cationized ferritin (CF) as a tracer. CF was rapidly internalized (after 5 min) in coated pits and vesicles that were labeled by antibodies against clathrin. The tracer was then delivered (after 15 min) to vacuoles and multivesicular bodies. These structures were labeled with A-Ly-M. These organelles were devoid of acid phosphatase activity. At later stages (after 30 min) CF was observed within larger structures that were strongly stained by A-Ly-M and displayed a strong acid phosphatase activity. These findings clearly indicate that A-Ly-M react with prelysosomal and lysosomal compartments involved in the endocytic pathway in cultured prolactin cells. The membrane of these structures therefore contains antigenic determinant(s) related to the 100,000-mol-wt polypeptide. Our results suggest that the prelysosomal structure stained by A-Ly-M may represent in GH3 cells the acidic prelysosomal compartment recently described in the early steps of endocytosis in other cell types (Tycko, B., and F. R. Maxfield, 1982, Cell, 28:643-651).
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PMID:Antibodies against a lysosomal membrane antigen recognize a prelysosomal compartment involved in the endocytic pathway in cultured prolactin cells. 397 94

The major glycoprotein of the human erythrocyte membrane has been isolated by treatment with lithium di-iodosalicylate and found to be a single polypeptide chain with a molecular weight of about 50,000. This molecule, which is 60% carbohydrate and 40% protein, carries multiple blood-group antigens, the receptors for influenza viruses, and various plant agglutinins. Four unique carbohydrate-containing peptides (alpha-1, alpha-2, alpha-3, and beta) are produced by tryptic digestion of the isolated glycoprotein; their order in the molecule has been determined by sequential tryptic digestion of intact erythrocyte membranes and partially digested glycoprotein fragments. Cleavage of the native protein with cyanogen bromide produces five fragments; two of these (C-5 and C-1) contain most of the carbohydrate in the molecule and are derived from the N-terminal half of the polypeptide chain. The nonpolar amino acids of this glycoprotein are located predominantly in the C-terminal fragment (C-2). Phytohemagglutinin conjugated to ferritin has been used to map the distribution of glycoprotein receptors over the surfaces of intact erythrocytes by freeze-etching and electron microscopy. This label localizes to sites on the membrane that overlie the intramembranous particles. These findings suggest that the glycoprotein is oriented at the cell surface with its oligosaccharide-rich N-terminal end exposed to the exterior, while its C-terminal segment interacts with other components in the interior of the membrane to form intramembranous particles.
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PMID:Chemical characterization and surface orientation of the major glycoprotein of the human erythrocyte membrane. 450 56

The iron storage protein ferritin is the principal yolk protein in oocytes of the snails Planorbarius corneus L. and Lymnaea stagnalis L. This report gives an account of the isolation procedure and of some properties of snail ferritins. The isolation procedure includes a heat-denaturation step, gel filtration on Sepharose 6B and two ultracentrifugation steps followed by electrophoresis. Ferritins from both snails are highly reminiscent of vertebrate and plant ferritins in terms of heat stability, absorption spectrum and ultrastructure, and both share common antigen determinants with horse spleen ferritin. In different electrophoresis systems snail ferritins display considerable heterogeneity and microheterogeneity. Electrophoresis in the presence of sodium dodecyl sulphate (SDS) yields two major polypeptides with molecular weights of 19 000 and 24 000, which are interpreted to be authentic subunits of the ferritin molecule. Different organs and tissues of the snails differ in subunit composition. Midgut gland ferritin consists predominantly of the 19 000 Mr polypeptide, while in embryos only the 24 000 Mr band was found. No carbohydrates or lipids could be detected by staining acrylamide gels. Results from SDS/acrylamide electrophoresis, electrophoresis under non-denaturing conditions on gradient gels and from isoelectric focusing indicate that the ferritins of both snails are composed of at least two different types of ferritin that are tissue-specific. One ferritin is typical of somatic tissue (midgut gland) and is most probably a homopolymer of the 19 000 Mr subunit. The other ferritin is typical of oocytes, but since it is an exogenous protein it is also encountered in the midgut gland (the presumed site of yolk synthesis) and the haemolymph. Vitellogenic ferritin is either a homopolymer of the 24 000 Mr subunit or is predominantly composed of it. So far, there is no evidence for a precursor-product relationship between the two subunits.
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PMID:Isolation and properties of vitellogenic ferritin from snails. 619 Aug 25

The biological and antigenic roles of glycosylation were investigated in the influenza hemagglutinin (HA) glycoprotein using the glycosylation inhibitor tunicamycin (TM). Under conditions where only the nonglycosylated form of HA was detected by immunoprecipitation and gel electrophoresis, the migration of glycoproteins to the cell surface was observed by immunofluorescence using either monospecific or monoclonal antibody to the HA polypeptide. Analysis of the surface fluorescence in TM-treated infected cells by a fluorescence-activated cell sorter (FACS) showed that all cells exhibited fluorescence in the complete absence of glycosylation. The relative amount of HA antigen on cell surfaces was found to be reduced by only 30-40% in TM-treated cells, and this reflected a similar reduction in intracellular synthesis. Electron microscopic studies using ferritin labeling also demonstrated that the nonglycosylated HA glycoprotein was present in significant amounts on surfaces of infected cells. Virions with nonglycosylated glycoproteins were purified, and were found to have an approximate 30-fold decrease in both hemagglutinin and neuraminidase specific activities. The possible role of oligosaccharides in antigenic variation among various H1N1 strains was investigated. Immunoprecipitation reactions involving five different monoclonal antibodies and five antigenic variants of A/USSR/90/77 revealed no major antigenic differences between the glycosylated and nonglycosylated forms of HA.
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PMID:Studies on the role of glycosylation in the functions and antigenic properties of influenza virus glycoproteins. 619 89

We evaluated whether assay of tissue polypeptide antigen (TPA) in sera is valuable for the determination of cancer stages compared to other tumor markers such as CEA, AFP, beta2-microglobulin, ferritin, and elastase-1. The study population consisted of cancer patients (33 gastric cancers, 7 colo-rectal cancers and 15 hepatomas), 169 patients with benign gastro-enteric diseases and 72 healthy volunteers. The percentage of positive cases for TPA (higher than 200 u/l) was 61% in gastric cancer, 71% in colo-rectal cancer and 87% in hepatoma. In certain non-cancerous conditions, such as gastric ulcer (active stage), acute hepatitis and chronic hepatitis, the TPA levels were increased over the level of healthy volunteers. There was no significant correlation between TPA and the other tumor markers. Our study suggests that TPA may be useful in the identification and evaluation of cancer patients.
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PMID:[Clinical study on tissue polypeptide antigen (TPA) as a tumor marker]. 620 29

Immunoreactivities of peptides purified after cleavage of human liver apoferritin are reported and discussed in relation to the known 3-dimensional and primary structures of homologous apoferritins. These studies point to 3 antigenic sites occupying continuous inter-helical regions of the polypeptide chains which lie on the surface of the apoferritin molecule. Other antigenic regions may encompass amino acids remote in the primary structure or belonging to different subunits.
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PMID:The location of antigenic sites on ferritin molecules. 620 51

Human epithelioid carcinoma A-431 cells are known to express unusually large numbers of receptors for the polypeptide hormone epidermal growth factor. The current studies demonstrate that this cell line also expresses 5- to 10-fold more low density lipoprotein (LDL) receptors per cell than either human fibroblasts or Chinese hamster ovary (CHO) cells. As visualized with an LDL-ferritin conjugate, the LDL receptors in A-431 cells appeared in clusters that were distributed uniformly over the cell surface, occurring over flat regions of the membrane as well as over the abundant surface extensions. Only 4% of the LDL receptors were located in coated pits. The LDL receptors in A-431 cells showed the same affinity and specificity as the LDL receptors in human fibroblasts and other cell types. In addition, they were subject to feedback regulation by sterols in the same manner as the LDL receptors in other cells. However, in contrast to other cell types in which the receptor-bound LDL is internalized with high efficiency, in the A-431 cells only a small fraction of the receptor-bound LDL entered the cell. In CHO cells approximately 66% of the LDL receptors were located over coated regions of membrane, and the efficiency of LDL internalization was correspondingly 10-fold higher than in A-431 cells. These findings support the concept that the rate of LDL internalization is proportional to the number of LDL receptors in coated pits and that the inefficiency of internalization in the A-431 cells is caused by a limitation in the ability of these cells to incorporate their LDL receptors into coated pits.
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PMID:Inefficient internalization of receptor-bound low density lipoprotein in human carcinoma A-431 cells. 625 81

Actin and the simian virus 40 viral structural polypeptide Vp1 are observed to be present on cytoskeletal fibers of virus-infected TC7 cells, when these antigens in detergent-extracted whole cell mounts were labeled by specific antibodies and colloidal gold particles coated with a second antibody. In both cases, actin and Vp1 were found associated with fibers and fiber-associated electron-dense materials. Patches or clusters of colloidal gold particles denoting the presence of either Vp1 or actin were found on fibers uniformly distributed throughout the cytoplasm. By using simultaneous decoration of the two antigens with colloidal gold particles of different diameters, it was shown that the majority of Vp1 appears attached to cytoskeletal fibers in association with cellular actin. When Vp1 and actin were decorated with Imposil and ferritin simultaneously in infected cells that were fixed first and then permeabilized with saponin, both labels were found in the same spatial domain of the cell cytoplasm. Thus, the colocalization of Vp1 and actin on the cytoskeletal framework seems to reflect their actual state in the living cells. The electron-dense material to which colloidal gold particles localize in our cytoskeletal preparations may be the remnants of subcellular structures with which actin and Vp1 are both associated in intact cells.
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PMID:Visualization of antigens attached to cytoskeletal framework in animal cells: colocalization of simian virus 40 Vp1 polypeptide and actin in TC7 cells. 630 16

In the serum of five patients with malignant germ cell tumor of the testis, prolactin as well as one or several of the gonadotropic, androgenic, estrogenic, and gestagenic hormones appeared to have the quality of tumor markers so that monitoring their serum level together with that of tissue polypeptide antigen, carcinoembryonic antigen, alpha-fetoprotein, and ferritin was useful. These compounds were determined by radioimmunoassay. Their serum concentration was often elevated although a constant pattern of findings or a relation to the severity of the disease was not observed. A corroboration of these results and an elucidation of their pathogenesis are necessary in a large number of patients.
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PMID:Serum prolactin, gonadotropins, androgens, estrogens, and gestagens in patients with malignant testicular germ cell tumor. 630 85


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