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

The coding regions of the cDNAs for cytoplasmic soma ferritin and secreted yolk ferritin from the snail Lymnaea stagnalis were inserted into the prokaryotic expression vector pEMBLex2. The vector directed the synthesis in Escherichia coli of soma ferritin up to a concentration of 15% of soluble proteins. Soma ferritin was expressed as the multimeric protein (480 kDa). Its similarity with natural soma ferritin was confirmed by PAGE, immunostaining and electron microscopy. Yolk ferritin was expressed in the form of inclusion bodies. Attempts to refold and assemble the purified yolk ferritin subunit in vitro failed. The yolk ferritin coding sequence was therefore inserted into the expression vector pMAL-p2. At a growth temperature of the bacterial cells of 23 degrees C and at an isopropyl beta-D-thiogalactopyranoside concentration of 50 microM, about 5% of the induced MalE-yolk-ferritin fusion protein was secreted into the periplasmic space and could be purified by affinity chromatography on amylose; the rest occurred as insoluble cytoplasmic inclusion bodies. Soluble MalE-yolk-ferritin fusion protein was capable of assembly into ferritin-like particles. Fully assembled yolk apoferritin shells (610 kDa) were obtained by digestion of these particles with proteinase K (yield: 180 micrograms yolk ferritin/l bacterial culture). Recombinant yolk ferritin was capable of taking up iron in vitro. Yolk ferritin (610 kDa) and soma ferritin (480 kDa) were run to the pore limit of a non-denaturing 5-20% PAGE gradient gel. Under these conditions, yolk ferritin had a higher mobility than soma ferritin (480 kDa) and therefore the yolk ferritin may have a rather compact structure. A 41-amino-acid-residue stretch of the insertion, a distinctive feature of the yolk ferritin subunit, was deleted by site-directed mutagenesis. The MalE-yolk-ferritin variant thus obtained was readily degradable by proteinase K and could not be assembled into ferritin-like particles. Therefore residues in the deleted peptide must be important for the maintenance of the native structure.
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PMID:Expression in Escherichia coli of a secreted invertebrate ferritin. 802 Apr 74

The purpose of this study was to demonstrate how single cell quantitative and subcellular metallomics inform us about both the spatial distribution and cellular mechanisms of metal buffering and homeostasis in primary cultured neurons from embryonic rat brain, which are often used as models of human disease involving metal dyshomeostasis. The present studies utilized synchrotron radiation X-ray fluorescence (SRXRF) and focused primarily on zinc and iron, two abundant metals in neurons that have been implicated in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Total single cell contents for calcium, iron, zinc, copper, manganese, and nickel were determined. Resting steady state zinc showed a diffuse distribution in both soma and processes, best defined by the mass profile of the neuron with an enrichment in the nucleus compared with the cytoplasm. Zinc buffering and homeostasis was studied using two modes of cellular zinc loading - transporter and ionophore (pyrithione) mediated. Single neuron zinc contents were shown to statistically significantly increase by either loading method - ionophore: 160 million to 7 billion; transporter 160 million to 280 million atoms per neuronal soma. The newly acquired and buffered zinc still showed a diffuse distribution. Soma and processes have about equal abilities to take up zinc via transporter mediated pathways. Copper levels are distributed diffusely as well, but are relatively higher in the processes relative to zinc levels. Prior studies have observed iron puncta in certain cell types, but others have not. In the present study, iron puncta were characterized in several primary neuronal types. The results show that iron puncta could be found in all neuronal types studied and can account for up to 50% of the total steady state content of iron in neuronal soma. Although other metals can be present in iron puncta, they are predominantly iron containing and do not appear to be associated with ferritin cages or transferrin receptor endosomes. The iron content and its distribution in puncta were similar in all neuron types studied including primary dopaminergic neurons. In summary, quantitative measurements of steady state metal levels in single primary cultured neurons made possible by SRXRF analyses provide unique information on the relative levels of each metal in neuronal soma and processes, subcellular location of zinc loads, and have confirmed and extended the characterization of heretofore poorly understood cytoplasmic iron puncta.
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PMID:Understanding metal homeostasis in primary cultured neurons. Studies using single neuron subcellular and quantitative metallomics. 2627 17

The iron storage protein, ferritin, is the major yolk protein in freshwater snails. In this report we show by in vitro labelling experiments that yolk ferritin of the snails Lymnaea stagnalis L. and Planorbarius corneus L. is an exogenous protein synthesized in the midgut gland and secreted into the hemolymph. Gonad and mantle tissue are inactive in the synthesis of yolk ferritin, but, together with the midgut gland, they synthesize another ferritin type (soma ferritin) which is not released into the hemolymph and which may be a housekeeping ferritin. Soma ferritin and yolk ferritin are not in a precursor/product relationship since subunits of both ferritins are synthesized as primary translation products in rabbit reticulocyte lysate programmed with poly (A)+ RNA from midgut gland and gonad. Results suggest that both ferritins are synthesized on different mRNAs (and possibly on different genes) so they may be regulated in a different way.
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PMID:On the origin of the yolk protein ferritin in snails. 2830 44