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)

The interactions of horse spleen ferritin and its derivative apoferritin with H+ ions were studied by potentiometric and spectrophotometric titration; to aid in data analysis, heats of ionization over a limited pH range and amide content were also determined. Per apoferritin subunit, all tyrosine and cysteine side chains, two of the nine lysine side chains and at least three of the six histidine side chains were found not to titrate; a preliminary but self-consistent analysis of the titration data is proposed. The titration curve of ferritin was identical with that of apoferritin in the pH range 5.5 to 3. In addition, under the conditions used, the reactivities of ferritin histidines to bromoacetate and of ferritin lysines to formaldehyde were identical with those in apoferritin. Above pH 8, a time-dependent titration of the ferritin core occurs which prevents comparison of the titration curves of the two proteins in this region. However, in the pH regions 5.5 to 7.5, two extra groups per subunit titrate reversibly in ferritin relative to apoferritin. Moreover, although the isoionic points of ferritin and apoferritin are identical in water, the isoionic point of ferritin is 0.5 pH unit lower than that of apoferritin in 0.16 to 1 M KCl. The different effects of KCl and NaCl on the two proteins indicate the presence of cation binding sites in ferritin that are absent in apoferritin and possibly also the presence of anion binding sites in apoferritin that are occupied in ferritin by anions of the core. The difference between the isoionic points of the two proteins in KCl has been interpreted to indicate the presence of approximately 2 phosphate residues per ferritin subunit which serve as cation binding sites and which are negatively charged at the isoionic point in KCl. These phosphates may also represent the additional residues that titrate in ferritin between pH 5.5 and 7.5, or may interact with positively charged residues on the inner surface of the ferritin shell, or both.
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PMID:Hydrogen ion interactions of horse spleen ferritin and apoferritin. 1 Dec 12

Cells from malignant and normal lines of human hematopoietic origin were studied for their surface charge characteristics with the use of the following criteria: 1) the electron microscopic appearance of cell membranes after labeling with cationized ferritin (CF) either before or after glutaraldehyde fixation, 2) electrophoretic mobility, 3) total sialic acid content, and 4) agglutinability with poly-L-lysine (PLL). CF induced a time-dependent redistribution of surface receptors in unfixed malignant cells but not in unfixed normal cells. After 10 seconds of labeling with CF, both normal and malignant unfixed cells showed a uniform and even labeling pattern. After 5 minutes of labeling, malignant cells exhibited a highly pronounced pattern of clusters and patches, as distinct from a random and even pattern exhibited by normal cells. Both normal and malignant cells after fixation exhibited an equivalent random and even labeling pattern with CF, independent of the duration of labeling. The malignant cells studied possessed less sialic acid, had a lower electric mobility, and were agglutinated more readily with PLL than were the normal cells.
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PMID:Surface charge characteristics of cells from malignant cell lines and normal cell lines of the human hematopoietic system. 31 Sep 7

Peripheral blood lymphocytes from patients with chronic lymphatic leukemia (CLL) and malignant lymphoma (ML) were tested for their surface negative charge characteristics and compared with lymphocytes from normal subjects by use of measurements of lymphocyte agglutination with a positively charged poly-L-lysine (PLL) molecule and by use of electron microscopic observation of lymphocytes labeled with cationized ferritin (CF). Unfixed lymphocytes from CLL and ML patients exhibited clustering and patching of CF particles, whereas normal lymphocytes had a uniform, continuous CF-labeling pattern. Lymphocytes from CLL patients had significantly higher agglutination with PLL than did normal lymphocytes.
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PMID:Surface charge characteristics of peripheral blood lymphocytes in chronic lymphatic leukemia and malignant lymphoma. 63 85

We have investigated the orientation of isolated fragments of Halobacterium halobium purple membrane (PM) adsorbed to poly-L-lysine-treated glass (PL-glass), by quanitative electron microscopy. Three lines of evidence support the conclusion that the cytoplasmic side of the membrane is preferentially absorbed. First, monolayer freeze-fracture reveals nonrandom orientation; more fracture faces (89%) are particulate than smooth. Second, the amount of each membrane surface present can be assayed using polycationic ferritin; 90% of all adsorbed membrane fragments are labeled. Third, it is possible to distinguish two surfaces, "cracked" (the extracellular surface) and "pitted" (the cytoplasmic surface) , in slowly air-dried, platinum-carbon-shadowed membranes. When applied under standard conditions, more than 80% appear cracked. Selection for the cytoplasmic by the cationic substrate suggests that the isolated PM, buffered at pH 7.4 and in the light, has a higher negative charge on its cytoplasmic surface than on its extracellular surface. Nevertheless, cationic ferritin (CF) preferentially adsorbs to the extracellular surface. Orientation provides a striking example of biomembrane surface asymmetry as well as the means to examine the chemical reactivity and physical properties of surfaces of a purified, nonvesicular membrane fragment.
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PMID:Oriented adsorption of purple membrane to cationic surfaces. 64 62

Cationic ferritin binds in a time and concentration dependent manner to all surfaces of ciliary ganglion neurons in culture except "mounds" and "veils". In chase experiments, bound ferritin clears from the cells surfaces and forms larger and larger patches, even at low temperatures. Binding of cationic ferritin is inhibited by poly-L-lysine, potentiated by poly-L-glutamate, and not affected by neruaminidase (acylneuraminyl hydrolase, EC 3.2.1.18), hyaluronidase (hyaluronoglucosidase, hyaluronate 4-glycanhydrolase, EC 3.2.1.35), or chondroitin ABC lyase (EC 4.2.2.4).
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PMID:Differential labeling of the cell surface of single ciliary ganglion neurons in vitro. 106 97

In apoferritin, but not in ferritin, 1.0 +/- 0.1 cysteine residue per subunit can be modified. In ferritin 3.3 +/- 0.3 lysine residues and 7.1 +/- 0.7 carboxyl groups per subunit can be modified, whilst the corresponding values for apoferritin are 4.4 +/- 0.4 lysine residues and 11.0 +/- 0.4 carboxyl groups per subunit. Modification of lysine residues which maleic anhydride and carboxyl groups with glycineamide in apoferritin which has been dissociated and denatured in guanidine hydrochloride leads to the introduction of 9.1 +/- 0.5 maleyl groups per subunit and 22.0 +/- 0.9 glycineamide residues per subunit. Whereas unmodified apoferritin subunit can be reassociated from guanidine hydrochloride to apoferritin monomer, the ability of maleylated apoferritin to reassociate is impaired. Apoferritin in which all the carboxyl groups have been blocked with glycineamide cannot be reassociated to apoferritin and exists in solution as stable subunits. The modification of one cysteine residue per subunit, of 3 or 4 lysine residues per subunit or of 7 carboxyl groups per subunit has no effect on the catalytic activity of apoferritin. In contrast the modification of 11 carboxyl groups per subunit completely abolishes the catalytic properties of the protein. We conclude that one or more carboxyl groups are essential for the catalytic activity of horse spleen apoferritin.
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PMID:Chemical modification as a probe of the topography and reactivity of horse-spleen apoferritin. 124 72

Commercial preparations of ferritin inhibited reticulocyte-lysate cell-free protein synthesis and disaggregated polyribosomes to monoribosomes and ribosomal subunits. These effects were prevented by addition of reduced glutathione (GSH) to the incubation medium, but ferritin did not lower GSH concentration in the lysates. The more purified the ferritin preparation, the less inhibition of protein synthesis was observed. These data suggested that the effect was due to a contamination of the ferritin with proteolytic activity. In confirmation of this proposal we demonstrated that there was protease activity in both the 2X and 5X crystalized ferritin preparations, with 2.5 times greater activity in the 2X preparation. The proteolytic activity in ferritin was inhibited by incubation with the protease inhibitor tosyl lysine chloromethyl ketone (TLCK). When an amount of trypsin equivalent to the protease activity of the ferritin was added to the incubation mixture, similar effects on protein synthesis and the ribosome-polyribosome component were found. Both GSH and TLCK prevented these effects of trypsin. These data suggest that the previously reported effect of ferritin on reticulocyte cell-free protein synthesis was due to contamination of the ferritin by a protease. It appears that ferritin does not play a direct role in the pathogenesis of sideroblastic anaemias.
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PMID:Ferritin and sideroblastic anaemias: inhibition of protein synthesis by protease contaminants in commercial preparations of ferritin. 125 40

A low-molecular-weight, non-transferrin-bound, Fe(III)-binding polypeptide has been isolated and purified from normal human cord and adult sera by gel-filtration and high-performance liquid chromatography. The polypeptide was traced isotopically with 59Fe(III)-chloride and high voltage paper electrophoresis. This Fe(III)-binding polypeptide has been partially characterized, and found to be biochemically distinct from other known Fe(III)-binding proteins, such as transferrin, lactoferrin and ferritin. Furthermore, the electrophoretic mobility and amino-acid composition distinguish the polypeptide from other physiological iron chelators such as a previously described Fe(III)-citrate complex. The polypeptide is highly hydrophilic, rich in lysine residues and phosphorylated. The observed positive charge of the polypeptide is suggested to originate from these lysine residues. The molecular mass of this polypeptide is estimated to be approx. 2500 Da, which is in close agreement with previous reports and is consistent with amino-acid analysis data. Cord serum levels of the polypeptide were significantly higher than adult serum levels. The degree of Fe(III) specificity and the function of the Fe(III)-polypeptide have not been ascertained at the present time. It is possible that the polypeptide may compete for Fe(III) with transferrin and is involved in the mobilization and transportation of iron by some as yet unknown mechanism.
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PMID:Iron(III)-binding polypeptide in human cord and adult serum: isolation, purification and partial characterization. 142 Mar 22

Polymorphonuclear leukocytes (PMNs) exhibit extensive directional migration (chemotaxis) and phagocytic activities. We have developed an in vitro model to evaluate the organization of the microtubule organizing center (MTOC) in PMNs as the latter interact with various substrata, including immobilized antigen-antibody complexes. PMNs were layered on poly-L-lysine substrata containing ferritin (PL+F) or ferritin-antiferritin complex (PL+F+AF) and the location of MTOCs was determined by indirect immunofluorescence of tubulin using conventional epifluorescence microscopy and confocal laser scanning microscopy. The MTOCs in the majority of the PMNs attached to PL+F occupied an apical location (81.29% +/- 3.34%), while in the majority of PMNs layered onto PL+F+AF, a basal location (79.37% +/- 5.26%) was observed. Following disruption of microtubules (MTs) by nocodazole before layering the cells on the substrata, the proportions of PMNs with apical MTOCs were 65.2% +/- 6.27% for PL+F and 47.2% +/- 4.1% for PL+F+AF substrata, while the proportions of PMNs with basal MTOCs were 26.11% +/- 8.89% for PL+F and 39.6% +/- 4.4 for PL+F+AF substrata. The results indicate that MTOCs in human PMNs in vitro (i) occupied a 'pre-defined' apical location; (ii) translocated to a 'newly defined' basal location upon stimulation with immobilized antigen-antibody complex; (iii) and depended on intact MTs for placement of MTOCs in both situations.
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PMID:Stimulus-dependent relocation of the microtubule organizing center in human polymorphonuclear leukocytes. 142 87

This study compared the effect of loading apoferritin either with ferrous ammonium sulfate in various buffers or with ceruloplasmin and chelated ferrous iron. It was shown that loading of apoferritin with ferrous ammonium sulfate was dependent on buffer and pH, and was directly related to the rate of iron autoxidation. The ceruloplasmin-dependent loading of apoferritin, however, was unaffected by these factors. Isoelectric focusing and amino acid analysis of the differently loaded ferritins showed that ferrous ammonium sulfate loading of apoferritin resulted in the depletion of the basic amino acids, lysine and histidine, probably as a result of protein oxidation. No significant differences in amino acid composition was noted for ceruloplasmin-loaded ferritin. Furthermore, ferritin loaded with ferrous ammonium sulfate released more iron than either native or ceruloplasmin-loaded ferritin when either paraquat or EDTA was used as an iron mobilizing agent. We suggest that the loading of apoferritin with ferrous ammonium sulfate occurred as a result of iron autoxidation and may result in oxidation of amino acids and loss of integrity of the protein, and that ceruloplasmin may act as a catalyst for the incorporation of iron into apoferritin in a manner more closely related to that occurring in vivo.
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PMID:In vitro loading of apoferritin. 153 76


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