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

Morphological studies were carried out on fibroblasts from chick embryo tendons, cells which have been used in a number of recent studies on collagen biosynthesis. The cells were relatively rich in endoplasmic reticulum and contained a well-developed Golgi complex comprised of small vesicles, stacked membranes, and large vacuoles. Techniques were then devised for preparing cell fragments which were penetrated by ferritin-antibody conjuates but which retained the essential morphological features of the cells. Finally, the new procedures were employed to develop further information as to how collagen is synthesized. As reported elsewhere, preliminary studies with ferritin-labeled antibodies showed that prolyl hydroxylase was found in the endoplasmic reticulum of freshly isolated fibroblasts and that procollagen is found in both the cisternae of the endoplasmic reticulum and the large Golgi vacuoles. In the experiments described here, the cells were manipulated so that amino acids continued to be incorporated into polypeptide chains but assembly of the molecule was not completed because hydroxylation of prolyl and lysyl residues was prevented. The results indicated that these manipulations produced no change in the distribution of prolyl hydroxylase. Examination of the cells with ferritin conjugated to antibodies which reacted with protocollagen, the unhydroxylated form of procollagen, demonstrated that protocollagen was retained in the cisternae of the endoplasmic reticulum during inhibition of the prolyl and lysyl hydroxylases. Assays for prolyl hydroxylase with an immunologic technique demonstrated that although the enzyme is found within the endoplasmic reticulum, it is not secreted along with procollagen. The observations provided further evidence for a special role for prolyl hydroxylase in the control of collagen biosynthesis.
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PMID:Further characterization of embryonic tendon fibroblasts and the use of immunoferritin techniques to study collagen biosynthesis. 16 30

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

On account of its easy access in aqueous solution to the two states ferrous (FeII) and ferric (FeIII), iron is ideally suited for the activation of molecular oxygen. It is, therefore, logical to seek links between the normal and pathological metabolism of iron and oxygen activation. The pathways of intracellular iron metabolism require changes in the oxidation state of iron both in its deposition in the storage form, ferritin, and in its mobilization from the storage form and use in the cell. Evidence is presented which shows that iron oxidation and deposition in ferritin involves activation of molecular oxygen with formation of a stable peroxo-complex as an intermediate in which the oxygen is bound between two iron atoms attached to adjacent polypeptide chains. The release of iron from ferritin is thought to involve reduction by a flavin, which is associated with the protein, and serves as a cofactor being alternately reduced by NADH or NADPH and oxidized by iron(III). The nature of the low-molecular-weight iron complex which serves to transfer storage iron to transferrin and to supply iron for intracellular use remains to be established. The consequence of excessive iron overload can be rationalized on the basis of oxidative free-radical reactions which provoke lesions typical of deregulated oxygen activation. In some cases these pathological defects can be reversed by iron chelators. Progress in the development of chelation therapy for iron overload are reviewed.
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PMID:Interactions between iron metabolism and oxygen activation. 25 65

The major protein associated with actin in the microfilament core of intestinal microvilli has been purified. This protein, for which we propose the name villin, has a polypeptide molecular weight of approximately 95,000. Two arguments suggest that villin may be the microvillus crossfilament protein that links the microfilament core laterally down its length to the cytoplasmic side of the plasma membrane. First, electron microscopy shows that crossfilaments stay attached to isolated membrane-free microvillus cores. Calculation of the expected abundance of the crossfilament protein shows that only villin is present in sufficient quantity to account for these structures. Second, decoration of microvillus cores by antibodies to either actin or villin, followed by ferritin-labeled second antibody in a sandwich procedure, results in specific labeling of the cores in both cases. The antivillin decoration, however, gives rise to a greater increase in diameter, in agreement with a model in which villin projects from the F-actin microfilament core. Villin is distinct from alpha-actinin, a protein suggested to be involved in membrane anchorage of microfilaments in nonmuscle cells. The two proteins differ in molecular weight. Specific antibodies against villin and alpha-actinin show no immunological crossreactivity. Immunofluorescence microscopy reveals that villin is located in the microvilli of the brush border whereas alpha-actinin is absent from the microvilli but is found in the terminal web. In addition, villin is not found in microfilament bundles of tissue culture cells, which are rich in alpha-actinin. Thus, villin and alpha-actinin appear to be immunologically and functionally different proteins.
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PMID:Villin: the major microfilament-associated protein of the intestinal microvillus. 28 75

Glycophorin A is the major sialoglycoprotein of the human erythrocyte membrane. Structural studies indicate that this molecule is made up of 3 domains composed of 2 hydrophilic segments which are separated by a region of 22 nonpolar amino acids. The N-terminal half of the molecule contains all the carbohydrate associated with this protein. Glycophorin A forms high-molecular-weight complexes which can be dissociated only under certain conditions. The site of subunit interaction is located within the hydrophobic segment, which serves both to mediate protein-protein and protein-lipid interactions within the bilayer membrane. Glycophorin A spans the membrane presumably as a dimeric complex with the carboxyterminal ends extending into the cytoplasm of the red cell. The transmembrane nature of the polypeptide chains finds strong support from the use of specific antibody-ferritin conjugates applied to thin sections of fixed and frozen intact cells. Preliminary information on the analysis of human red cell variants which may lack some or all of the sialoglycopeptides are consistent with the presence in normal cells of a second sialoglycoprotein, provisionally labeled glycophorin B.
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PMID:Structural analysis of a membrane glycoprotein: glycophorin A. 60 96

Ferritin was isolated from the seeds of pea (Pisum sativum) and lentil (Lens esculenta). The homogeneity of the phytoferritins was established by polyacrylamide-gel electrophoresis. The subunit molecular weights were respectively 20 300 and 21 400 for hte pea and lentil proteins. A neutron low-angle scattering study established the molecular weight of the oligomer as 480 000 for pea apoferritin and 510 000 for lentil apoferritin. Although the quaternary structure of 24 polypeptide chains is preserved, the phytoferritins have a larger cavity in the interior than mammalian ferritins and can thus potentially store 1.2-1.4 times as much iron. The amino acid composition of the phytoferritins show some similarities to those of mammalian apoferritins; tryptic 'fingerprinting' reveals that there are many differences in the amino acid sequence of plant and mammalian apoferritins.
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PMID:Isolation and characterization of phytoferritin from pea (Pisum sativum) and Lentil (Lens esculenta). 65 49

The surface complex of Euglena has been examined intact and after isolation and purification by the use of mild sonication to disrupt cells. In intact cells the surface complex (pellicle complex) is oriented in a series of parallel ridges and grooves, and possesses among other components a characteristic group of four to seven microtubules. Isolated pellicles retain the ridge and groove pattern but no microtubules are present. Isolates yielded at least three major polypeptides on SDS acrylamide gels; one or more of the polypeptides are postulated to be identical with a submembrane layer present in both intact and isolated pellicles; one polypeptide appears to be in or on the surface membrane. Antibodies directed against the isolated pellicles were conjugated directly or indirectly to fluorescein, latex spheres, or ferritin. In appropriate experiments with these antibody conjugates, it has been found that antigenic sites are immobile and that new antigenic sites (daughter strips) are inserted between parental strips in replicating cells. These results together with direct observation of daughter strips by transmission electron microscopy suggest that surface growth in Euglena occurs by intussusception. Microtubules associated with the pellicle complex are postulated to play a role in the development of new daughter strips, and possibly also in cell movements.
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PMID:Immunological and structural evidence for patterned intussusceptive surface growth in a unicellular organism. A postulated role for submembranous proteins and microtubules. 81 92

Corbicula sandai apoferritin possesses physical properties different from apoferritins of other species. The native molecular weight was estimated from its s020,w of 18.7 S to be about 503 000. Empirical molecular weight estimation methods in denaturing solvents yielded a molecular weight estimate for the constituent polypeptide chain of 23 000. The circular dichroic spectrum of C. sandai apoferritin was significantly different from other apoferritins and it was immunologically unreactive with rabbit anti-human ferritin antisera.
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PMID:The properties of Corbicula sandai apoferritin. 85 6

Between 30 and 50% of pig lymphocyte plasma membrane vesicles were not bound by concanavalin A (Con A)-Sepharose. Various results suggest that the Con A-unretarded fraction represents "inside-out" membrane vesicles. First, an alternative cell surface ligand, anti-lymphocytic serum, gave a similar fractionation to Con A. Second, lack of binding by Con A was not due to lack of carbohydrate or to masking of carbohydrate by extraneous protein, because the unfractionated membrane and the unretarded fraction had similar carbohydrate and polypeptide compositions. Third although the carbohydrate of the unretarded membrane vesicles was accessible to 125I-labelled Con A and to release by soluble trypsin, it was not accessible to ferritin-Con A or trypsin-Sepharose. Fourth, antisera against the external surface of the Con A-unretarded vesicles strongly agglutinated the unretarded membrane, but caused negligible agglutination of whole lymphocytes. When attached to Sepharose these antisera bound all of the Con A-unretarded fraction, but failed to bind the membrane that adhered to Con A-Sepharose.
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PMID:Preparation of inside-out vesicles of pig lymphocyte plasma membrane. 95 79

A new human extrahepatic bile duct carcinoma cell line (KMBC) was established from a serially transplanted tumor in nude mice that originated from a surgically resected tumor from a 73-year-old Japanese man; the cell line has been maintained for 5 five years. KMBC cells proliferate in a monolayered sheet with a population doubling time of 30 hours. Chromosome number was distributed in a range from 37 to 44, with modal numbers of 40 and 41. KMBC cells and the reconstituted tumor in a nude mouse showed moderately to poorly differentiated adenocarcinoma and possessed various functional characteristics of extrahepatic bile duct carcinoma. KMBC cells secreted carbohydrate antigen 19-9, tissue polypeptide antigen, carcinoembryonic antigen, ferritin, beta 2-microglobulin, fibronectin, and alpha 2-macroglobulin and produced glutamic oxaloacetic transaminase and alkaline phosphatase. KMBC is the second established cell line that originated from a human extrahepatic bile duct carcinoma in the world literature, and it will be applicable to various experiments.
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PMID:Establishment and characterization of a new human extrahepatic bile duct carcinoma cell line (KMBC). 131 90


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