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

An affinity-purified plant lectin from Ricinus communis (RCAII) was shown to exhibit differential toxicity toward SV40-transformed 3T3 fibroblasts grown in vitro. When macromolecular synthesis was examined in SV3T3 and 3T3 cells, RCAII suppressed cell protein synthesis in the transformed line at lower concentrations (1/50 to 1/100) compared to the 3T3 line, and these effects were blocked by the RCAII inhibitors D-galactose or lactose. RNA and DNA synthesis and L-leucine transport were relatively unaffected by RCAII concentrations (greater than 1 mug/ml) that completely suppressed protein synthesis in both cell lines. The RCAII-mediated inhibition of cell protein synthesis required incubation times longer than 60 min, but quantitative cell binding studies with 125-I-RCAII indicated that the lectin binds to maximal levels in approximately 5 to 10 min, even at 4 degrees. During 10-min labeling experiments with 125-I-RCAII (1 mug/ml), it was demonstrated that the cell-bound lectin could be almost quantitatively removed from cells up to an additional 15 min after labeling without subsequent inhibition of protein synthesis. However, longer incubation times (greater than 30 min) after RCAII cell labeling and washing resulted in incomplete removal of cell-bound lectin (less than 20 to 30% of cell-bound lectin could be removed after a 60-min incubation). The longer incubation times (greater than 60 min) also resulted in almost complete inhibition of protein synthesis. Ferritin-conjugated RCAII (ferritin-RCAII) was used to follow the fate of the cell-bound lectin. Ferritin-RCAII bound rapidly (less than 10 min) to SV3T3 cell surfaces and could be blocked from labeling with lactose. After a 10-min incubation at 4 degrees in ferritin-RCAII solutions, the ferritin label was exclusively located at the extracellular surface in a random distribution. After washing and incubation at 37 degrees, the ferritin-RCAII induced clustering of its receptors (15 to 30 min) and eventually induced endocytosis (30 to 60 min). Further incubation (greater than 60 min) resulted in a predominantly intracellular localization of ferritin-RCAII inside endocytotic vesicles and free in the cell cytoplasm. That RCAII acts directly on protein synthesis after cell entry was confirmed with rabbit reticulocyte and mouse Krebs II ascites S30 cell-free protein synthesis system in diameter wit
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PMID:Mechanism of cell entry and toxicity of an affinity- purified lectin from Ricinus communis and its differential effects on normal and virus-transformed fibroblasts. 16 59

A technique employing ferritin-conjugated antibody has been developed to visualize specific protein-DNA complexes in the electron microscope and has been used to demonstrate the preferential binding of simian virus 40 (SV40) T antigen at or near the origin of replication of SV40 DNA, 0.67 fractional length clockwise from the EcoRI restriction endonuclease cleavage site. urified covalently closed supercoiled circles of SV40DNA were treated with partially purified T antigen and the complex was stabilized by crosslinking with glutaraldehyde. Hamster antiT antigen gamma-globulin, ferritin-labeled goat anti-hamster gamma-globulin, and glutaraldehyde were then added sequentially. The location of the bound ferritin cores was measured with respect to the EcoRI cleavage site and the orientation of the cores relative to the ends of the DNA was determined with respect to the locations of Escherichia coli DNA unwinding protein, which binds to covalently closed supercoiled SV40 DNA at either of two preferred sites, 0.46 or 0.90 fractional length clockwide from the EcoRI cleavage site.
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PMID:T antigen binds to simian virus 40 DNA at the origin of replication. 16 17

A modification of previously described methods of electron microscopic gene mapping and of gene enrichment based on the avidin-biotin interaction is presented. The modification consists of coupling cytochrome-c instead of pentane diamine to the oxidized 2', 3' terminus of an RNA by Schiff base formation and BH-4 reduction. The RNA-cytochrome-c conjugate is purified by a simple chromatographic procedure; several biotins are attached to the cytochrome moiety by acylation. The extended arm between biotin and RNA gives efficient electron microscopic gene mapping of DNA:RNA-biotin hybrids with avidin-ferritin and avidin-polymethacylate sphere labels and efficient gene enrichment by buoyant banding of DNA:RNA-biotin:avidin-spheres in CsCl. A 1400 fold enrichment (thus, 25% pure) and a 90% yield of long Drosophila DNA strands with 5S RNA genes is achieved.
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PMID:Gene mapping and gene enrichment by the avidin-biotin interaction: use of cytochrome-c as a polyamine bridge. 20 10

ColE1 DNA has been allowed to react in vitro with N-acetoxy-N-2-[14C]acetylaminofluorene in the range of 0-15 N-2-[14C]acetylaminofluorene residues bound per molecule of DNA, at the C8 of guanine residues. Purified rabbit antibodies to both N-2-(guanosine-8-yl)-acetylaminofluorene and native DNA that had reacted with N-acetoxy-N-2-acetylaminofluorene were shown by electron microscopy to recognize specifically the acetylaminofluorene-modified ColE1 DNA. The antibodies bound to DNA were visualized either per se or after reaction with goat anti-rabbit immunoglobulins coupled with ferritin. There was a linear relationship between the average number of antibodies bound per DNA molecule and the number of N-2-(deoxyguanosine-8yl)-acetylaminofluorene residues per DNA molecule. The slope of this straight line was equal to 0.4. Due to the bivalence of the immunoglobulins one would expect a value of 0.5; we actually observed an important fraction of the bound antibodies crosslinking two parts of the same (or of another) DNA molecule.
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PMID:Electron microscopic visualization of N-acetoxy-N-2-acetylaminofluorene binding sites in ColE1 DNA by means of specific antibodies. 29 3

A complex containing the minor coat protein or adsorptionprotein (A protein) of bacteriophage fl has been solubilized from the fl virion, using the detergent deoxycholate. This complex was resolved from the fl DNA and from the fl major coat protein, or B protein, by gel filtration in the presence of deoxycholate. The A protein complex migrated as a single band on sodium dodecyl sulfate-urea-polyacrylamide gels corresponding to a molecular weight of 60 000. Analysis of the amino acid composition and amino terminal residues of this preparation indicates that the preparation contains a 20% contamination of additional protein species. Antibody against purified fd A protein is cross-reactive with deoxycholate-purified fl A protein and with fl phage. Electron microscopic observation of negatively stained complexes of fl phage with this anti-fd A protein antibody and ferritin conjugated goat anti-rabbit IgG antibody revealed phages with ferritin particles at their termini or complexes of two or more phages joined together at one end by ferritin, indicating that the complex of A protein molecules is located at one end of the filamentous fl virion.
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PMID:Adsorption protein of bacteriophage fl: solubilization in deoxycholate and localization in the fl virion. 32 64

A method is described for indirect electron microscopic visualization and mapping of tRNA and other short transcripts hybridized to DNA. This method depends upon the attachment of the electron-dense protein ferritin to the RNA, the binding being mediated by the remarkably strong association of the egg white protein avidin with biotin. Biotin is covalently attached to the 3' end of tRNA using an NH2(CH2)5NH2 bridge. The tRNA-biotin adduct is hybridized to complementary DNA sequences present in a single stranded non-homology loop of a DNA:DNA heteroduplex. Avidin, covalently crosslinked to ferritin, is mixed with the heteroduplex and becomes bound to the hybridized tRNA-biotin. Observation of the DNA:RNA-biotin:avidin-ferritin complex by electron microscopy specifically and accurately reveals the position of the tRNA gene, with a frequency of labeling of approximately 50%.
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PMID:Electron microscopic visualization of tRNA genes with ferritin-avidin: biotin labels. 34 43

Transformation for capsular-types (A and B) between four Staphylococcus aureus strains was attempted using a serum-soft agar technique to distinguish the capsular-type. DNA preparations from the Smith diffuse strain (capsular-type A) transformed strain NS58C (unencapsulated variant of capsular-type B) to type A. The strain NS58C required Ala- and His-, however, the two transformants tested were Ala+ and His+. These properties coincided with those of the donor strain just as the following characters of the transformants, which are quite different from the untransformed recipient cells: i) negative clumping factor reaction, ii) diffuse-type growth in serum-soft agar, and iii) high mouse virulence. The change to capsular-type A was antigenically comfirmed by electronmicroscopy using ferritin conjugated anti-capsular antibody.
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PMID:Encapsulation by transformation of strains of Staphylococcus aureus determined by the serum-soft agar technique. 37 20

Antibodies elicited in rabbits by chromatin and by purified histone H2B have been used to study the structure of chromatin by immunoelectron microscopy. Chromatin spread on grids reveals a structure of closely packed spherical particles with an average diameter of 104 A, arranged either in clusters or in linear arrays of beads, some of which have a supercoil-like arrangement. No DNA strings connecting the beads could be observed. Upon antibody binding, the diameter of the particles increases up to 300 A. This size is compatible with a model where one layer of gamma globulin molecules 110 A long encircles a sphere of chromatin 100 A in diameter. The presence of rabbit gamma globulins on the enlarged beads has been verified by the addition of ferritin-labeled goat anti-rabbit gamma globulins. Anti-chromatin sera which react with nonhistone proteins but not with free histones or DNA react with more than 95% of the beads; this suggests that most of the beads contain nonhistone proteins. Since the number of nonhistone proteins is large, it is improbable that each sphere contains a full complement of these proteins. We therefore suggest that the various chromatin spheres contain different types of nonhistone proteins. About 90% of the chromatin spheres reacted with antibodies to histone H2B, suggesting the most of the chromatin beads contain this type of histone.
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PMID:Chromatin structure visualization by immunoelectron microscopy. 95 84

The 4S RNA genes in HeLa mitochondrial DNA (mtDNA) have been mapped by electron microscopy using the electron-opaque label ferritin. This method is based on the high affinity interaction between the protein, avidin,and biotin. 4S RNA, covalently coupled to biotin, was hybridized to single-stranded mtDNA. The hybrids were then labeled with ferritin-avidin conjugates. The positions of ferritin-labeled 4S RNA genes were determined relative to the rRNA genes on both heavy (H) and light (L) strands of mtDNA. This region was recognized as a duplex segment after hybridization either with rRNA in the case of H strands or with DNA complementary to rRNA in the case of L strands. Our studies suggest that at least nineteen 4S RNA genes are present in the HeLa mitochondrial genome. On the H strand, we have confirmed the nine map positions found in a previous electron microscope mapping study (Wu et al., 1972) and obtained evidence for three additional 4S RNA genes. On the L strand, seven 4S RNA genes have been mapped. The nineteen genes are distributed more or less uniformly around the genome. There is a pair of closely spaced genes, approximately 150 nucleotides apart, on the H strand, and another closely spaced pair on the L strand.
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PMID:An electron microscope study of the relative positions of the 4S and ribosomal RNA genes in HeLa cells mitochondrial DNA. 97 42

The generation of deleterious activated oxygen species capable of damaging DNA, lipids, and proteins requires a catalyst such as iron. Once released, ferritin iron is capable of catalyzing these reactions. Thus, agents that promote iron release may lead to increased oxidative damage. The superoxide anion formed enzymatically, radiolytically, via metal-catalyzed oxidations, or by redox cycling xenobiotics reductively mobilizes ferritin iron and promotes oxidative damage. In addition, a growing list of compounds capable of undergoing single electron oxidation/reduction reactions exemplified by paraquat, adriamycin, and alloxan have been reported to release iron from ferritin. Because the rapid removal of iron from ferritin requires reduction of the iron core, it is not surprising that the reduction potential of a compound is a primary factor that determines whether a compound will mobilize ferritin iron. The reduction potential does not, however, predict the rate of iron release. Therefore, ferritin-dependent oxidative damage may be involved in the pathogenesis of diseases where increased superoxide formation occurs and the toxicity of chemicals that increase superoxide production or have an adequate reduction potential to mobilize ferritin iron.
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PMID:Ferritin as a source of iron for oxidative damage. 145 89


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