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

Thyroid hormone (T3) regulates the expression of rat TSH beta-subunit (TSH beta) mRNA, in part, at the posttranscriptional level, by reducing the half-life of TSH beta mRNA. The mechanism(s) mediating this alteration in mRNA stability are unknown, but previous work indicates that labile protein(s) are involved. The majority of cis-acting elements identified to date that have been implicated in the regulated destabilization of mRNAs have been located in the 3'-untranslated region (3'-UTR) of the mRNA. The 3'-UTR of rat, murine, and human TSH beta mRNA is highly conserved, and within this region is a 12-nucleotide consensus sequence, which is shared by the 3'-UTR of several other genes with unstable mRNAs. We reasoned that this homologous region could represent a binding motif for specific trans-acting RNA-binding protein(s), and that identification and characterization of such trans-acting factor(s) may provide critical insight into the mechanisms underlying T3-induced changes in TSH beta mRNA stability. Utilizing the RNA electrophoretic mobility shift assay and analysis of UV cross-linked RNA-protein complexes, a cytoplasmic trans-acting factor of approximately 80-85 kilodaltons was identified from rat pituitaries and several cell lines that binds in a sequence-specific manner to the 3'-UTR of rat TSH beta mRNA. Using competitive antisense oligonucleotides, the predominant binding site was mapped to the first 41 nucleotides of the 3'-UTR, which includes the consensus region. However, sequence upstream of the consensus was also shown to be important for binding. Using RNA electrophoretic mobility shift assay, two mRNAs containing sequence homology with the consensus region, c-erbA alpha-2 and a rat ferritin pseudogene, were shown to specifically compete with rat TSH beta mRNA for binding of this factor. Remarkably, the binding activity of this factor was regulated positively by T3 within 4 h, but only with rat pituitary extracts. These data suggest that in addition to binding rat TSH beta mRNA in a sequence-specific and T3-regulated manner, this novel trans-acting RNA-binding protein may also bind to other cytoplasmic mRNAs involved in diverse intracellular processes.
Mol Endocrinol 1995 Mar
PMID:Regulated specific protein binding to a conserved region of the 3'-untranslated region of thyrotropin beta-subunit mRNA. 777 83

Pollen from perennial rye grass (Lolium perenne) is a major cause of type I allergies worldwide. It contains complex mixtures of proteins, among which Lol p II is a major allergen. Previously, we have reported the cloning and sequencing of Lol p II and its expression in fusion with the heavy chain of human ferritin as carrier polypeptide (Sidoli et al., 1993, J. biol. Chem. 268, 21819-21825). Here, we describe the expression, purification and characterization of a recombinant Lol p II overproduced as a non-fusion protein in the periplasm of E. coli. The recombinant allergen was expressed in high yields and was easily purified in milligram amounts. It competed with the natural Lol p II for binding to specific IgE, and it induced allergic responses in skin prick tests, indicating to be immunologically analogous to the natural protein. Biochemical analyses indicate that recombinant Lol p II is a highly stable and soluble monomeric molecule which behaves like a small globular protein.
Mol Immunol 1995 May
PMID:Recombinant allergen Lol p II: expression, purification and characterization. 778 53

Xanthine oxidase exhibits ferroxidase activity and previously has been shown to catalyze the oxidative incorporation of iron into apotransferrin, the iron transport protein of plasma. These studies demonstrate that xanthine oxidase also efficiently promotes the oxidative incorporation of iron into apoferritin, the major iron storage protein of vertebrates, and that the ferroxidase activity of intestinal xanthine oxidase could be important in determining the fraction of iron within the intestinal mucosa cell partitioned to ferritin versus the iron that remains in a transient pool for rapid transport to plasma.
Biochem Mol Biol Int 1994 May
PMID:Xanthine oxidase: an efficient promoter of the iron loading of apoferritin. 795 Oct 57

In the lobster, most of the radionuclides ingested with contaminated food are concentrated in the digestive gland. Americium-241 accumulation in the hepatopancreas of the lobster was studied during the digestive cycle. Fractionations of cytosols at different times after ingestion of radioactive preys were performed by gel permeation chromatography to determine the distribution of 241Am in the different macromolecular components. 241Am was associated with ferritin during the whole digestive cycle. This observation suggests a correlation between 241Am distribution pathways and iron metabolism. The distribution of 241Am present in the other cytosolic proteins followed two major steps of accumulation which may be correlated to the evolution of the two main cellular types playing an important role in the digestive cycle (B and R type cells).
Biochem Mol Biol Int 1994 Aug
PMID:Biodynamic study of americium-241 accumulation in the cytosol of the hepatopancreas of the lobster Homarus gammarus. 798 52

During soybean (Glycine max) nodule development, induced ferritin mRNA concentration remains elevated while the protein concentration decreases 4- to 5-fold (M. Ragland and E.C. Theil [1993] Plant Mol Biol 21: 555-560). Investigation of posttranscriptional regulation of nodule ferritin during development showed that ferritin mRNA was efficiently translated based on polyribosome size in vivo, protein synthesis (0.8% of total protein) in vitro, and protein synthesis in intact nodules. Ferritin, a plastid protein, was processed in both immature and mature nodules. In chimeric mRNA, soybean ferritin mRNA sequences blocked the function of the iron regulatory element (IRE), the cis regulatory element of animal ferritin mRNA; the IRE regulates chimeric animal mRNAs. The absence of translational regulation of ferritin in plants contrasts with ferritin regulation in animals. Thus, ferritin regulation has diverged during evolution, whereas structure of the mature protein has been conserved. Ferritin in mature soybean nodules is apparently regulated after translation, possibly in analogy with such plastid proteins as chlorophyll-binding proteins D1, CP43, LHCI, and LHCII, the small subunit of ribulose-bisphosphate carboxylase, and apoplastocyanin. An autocatalytic mechanism observed in vivo for degradation of plastid protein D1 and in vitro for pea ferritin during iron release could explain the ferritin decreases in mature nodules.
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PMID:Posttranscriptional regulation of ferritin during nodule development in soybean. 811 47

Lactic acid 4 mM acted as a lipoperoxidant by increasing production of thiobarbituric acid-reactive substances (TBARS) in rat kidney slices and homogenates. This effect occurred mainly when slices and homogenates were incubated in a pH 5.4 medium conductive to full expression of compound acidity. TBARS increase was only slight when incubation was performed in Krebs buffer, pH 7.4. Moreover, sodium lactate 4 mM increased TBARS production only when homogenates were incubated in the pH 5.4 medium. Deferoxamine (1 mM) inhibited the prooxidant effect of lactic acid 4 mM, and TBARS increase was correlated with iron release. The iron mobilized may come from reserves where it is weakly bound or from ferritin; and ascorbic acid, present in low quantities in kidney, might trigger the release of this product.
Biochem Mol Biol Int 1993 Nov
PMID:Iron- and lactic acid-induced lipid peroxidation in rat kidney homogenates and slices. 811 16

Helicobacter pylori is a Gram-negative bacterium that infects the human gastric mucosa, causes gastritis and contributes to the development of peptic ulcers and gastric cancer. To facilitate molecular genetic analysis of this pathogen, we constructed a approximately 20-fold redundant cosmid library and physical/genetic map of strain NCTC11638. Genomic DNA fragments were cloned into the cosmid vector Lorist6, and clones were ordered by hybridization with several types of probes: (i) ends of cloned DNAs; (ii) chromosomal Notl digest fragments; (iii) cosmids containing Notl sites; and (iv) specific genes. Seven hundred and fifty-one cosmids were mapped to one of three contigs covering > 90% of the chromosome, and are represented by a 68-cosmid miniset. The order of cosmids was confirmed and extents of overlap among them were estimated by restriction analysis. All currently known H. pylori genes were mapped, including those for a cytotoxin (vacA), cytotoxin-associated protein (cagA), urease and regulatory functions (ureAb, ureD and ureH), catalase (katA), major and minor flagellins (flaA and flaB), heat-shock (stress) and chaperone proteins (dnaK, htA, hspB (groEL)), prokaryotic ferritin (pfr), an adhesin subunit (hpaA), a surface protein (26 kDa), and 16S and 23S ribosomal RNAs (two genes each). The orientations of eight genes or clusters were determined, and two repetitive sequences were also found. The gene order and rRNA gene copy number determined here differed from that reported for an unrelated strain, which suggests considerable flexibility in H. pylori genome organization.
Mol Microbiol 1994 Feb
PMID:Ordered cosmid library and high-resolution physical-genetic map of Helicobacter pylori strain NCTC11638. 815 75

Mammalian ferritins are 24-meric proteins composed of variable proportions of H and L-subunits. The L-chain, in contrast to the H-chain, lacks detectable ferroxidase activity, and its role in ferritin iron incorporation is unclear. In this study, apoferritins were subjected to iron loading with large iron increments to favour spontaneous iron hydrolysis. The homopolymers of the wild-type H-chain, and of a mutant H-chain with an inactivated ferroxidase centre, formed massive protein aggregates, while the L-chain homopolymers remained mostly soluble. The difference between H and L-ferritins was not related to the rate of iron oxidation or to the presence of preformed iron cores. Heteropolymers were constructed in vitro by co-renaturing different proportions of the H-chain with the L-chain or mutant H-chain with an inactivated ferroxidase centre. After loading with high iron increments, protein aggregation of the heteropolymers was reduced when the L-chain content was above 70 to 80%, either in combination with the wild-type H-chain or with the inactivated mutant H-chain. Under acidic conditions (pH 5.5, 1000 Fe atoms per molecule) the heteropolymers with about 20% H and 80% L-chains incorporated three to fourfold more iron into soluble 24-mers than the homopolymers. The data indicate that ferritins with more than 18 L-chains per molecule have the capacity to lower non-specific iron hydrolysis in bulk solution. This property is possibly due to a specific attraction of the incoming oxidized iron into the cavity and may be related to an effect of the L-chain on the cavity microenvironment. It is concluded that under high iron increments the ferritins with high L:H-chain ratios are the most efficient in incorporating iron, and this goes some way to explain why iron storage tissues contain L-rich isoferritins.
J Mol Biol 1994 May 20
PMID:The role of the L-chain in ferritin iron incorporation. Studies of homo and heteropolymers. 818 40

Primary cell cultures of mouse ventricular myocardium were infected with Trypanosoma cruzi, to study the consequences of T. cruzi-muscle cell interaction on the rate of spontaneous contractions, on the responses to norepinephrine, and on action potential parameters. Single cells or small cell groups of infected cultures were subjected to pharmacological and electrophysiological experiments. In concentrations ranging from 1 nM to 100 microM, norepinephrine exerted positive or negative chronotropic effects mediated by alpha-adrenergic receptors. A significant number of infected cells (25%) did not respond to the agonist. Two days after infection the cultures exhibited a higher frequency of spontaneous contractions (20%), paralleled by an increase in firing rate and a decrease in the action potential duration without significant changes in maximum diastolic potential and action potential amplitude. A decrease in alpha-adrenergic receptor-mediated positive chronotropic response to norepinephrine was also observed in 2-day infected cells. Cells made to phagocyte ferritin particles showed an increase in the rate of spontaneous contractions, but no changes in the positive chronotropic responses to norepinephrine. In conclusion, these observations show that during acute infection with T. cruzi, there are alterations in automaticity and in the chronotropic responses to norepinephrine, whose mechanisms are related to the process of parasite endocytosis by the cardiac cells.
J Mol Cell Cardiol 1993 Oct
PMID:Heart muscle cells acutely infected with Trypanosoma cruzi: characterization of electrophysiology and neurotransmitter responses. 826 57

Riboflavin deficiency in rats resulted in a reduction in the transfer of 59Fe from an intragastric dose to plasma compared to age-matched or weight-matched controls. The uptake of iron by brush-border membrane vesicles made from intestinal mucosa of riboflavin-deficient rats was much less than identically-prepared vesicles from control groups. Although the mucosal content of 59Fe was smaller in riboflavin-deficient rats thirty minutes after dosing, the relative distribution of 59Fe between the mucosal iron-binding proteins, ferritin and transferrin, was not changed compared to the control groups. These studies suggest that the impairment in iron absorption in riboflavin deficiency is primarily the result of a reduced uptake of iron into the mucosal cell and not a redistribution of iron between iron-binding proteins inside the mucosal cell.
Biochem Mol Biol Int 1993 May
PMID:Comparison of changes in the uptake and mucosal processing of iron in riboflavin-deficient rats. 835 36


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