The release of iron from horse spleen ferritin to 1,10-phenanthroline.
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ABSTRACT:
SUBMITTER: Hoy TG
PROVIDER: S-EPMC1166081 | biostudies-other | 1974 Jan
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Ferritin-Fe(III) was rapidly and quantitatively reduced and liberated as Fe(II) by FMNH(2), FADH(2) and reduced riboflavin. Dithionite also released Fe(II) from ferritin but at less than 1% of the rate with FMNH(2). Cysteine, glutathione and ascorbate gave a similar slower rate and yielded less than 20% of the total iron from ferritin within a few hours. The reduction of ferritin-Fe(III) by the three riboflavin compounds gave complex second-order kinetics with overlapping fast and slow reactions. The fast reaction appeared to be non-specific and may be due to a reduction of Fe(III) of a lower degree of polymerization, equilibrated with ferritin iron. The amount of this Fe(3+) ion initially reduced was small, less than 0.3% of the total iron. Addition of FMN to the ferritin-dithionite system enhanced the reduction; this is due to the reduction of FMN by dithionite to form FMNH(2) which then reduces ferritin-Fe(III). A comparison of the thermodynamic parameters of FMNH(2)-ferritin and dithionite-ferritin complex formation showed that FMNH(2) required a lower activation energy and a negative entropy change, whereas dithionite required 50% more activation energy and showed a positive entropy change in ferritin reduction. The effectiveness of FMNH(2) in ferritin-Fe(III) reduction may be due to a specific binding of the riboflavin moiety to the protein portion of the ferritin molecule.
| S-EPMC1168386 | biostudies-other
Project description:Horse spleen ferritin is shown to bind haem to generate a haemoprotein, named herein haemoferritin. A total of 14-16 haem molecules are bound per 24 subunits of ferritin. The molecular mass of the non-haem-iron-free haemoferritin has been determined to be 420 +/- 40 kDa, indicating that haem binding does not lead to dissociation of the 24 subunits that comprise the ferritin molecule. The functional role of the bound haem has been investigated with respect to the release of iron from the non-haem iron core. The bound haem is shown to increase the rate of iron release in a reductive assay system. In the absence of haem the rate of iron release depends on the redox potential of the reductant, but in the presence of haem the rate is largely independent of the reductant and is faster than the rate for the haem-free ferritin. These data haem, but in the presence of haem electron transfer is not rate-limiting.
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Project description:Native electron capture dissociation (NECD) is a process during which proteins undergo fragmentation similar to that from radical dissociation methods, but without the addition of exogenous electrons. However, after three initial reports of NECD from the cytochrome c dimer complex, no further evidence of the effect has been published. Here, we report NECD behavior from horse spleen ferritin, a ?490 kDa protein complex ?20-fold larger than the previously studied cytochrome c dimer. Application of front-end infrared excitation (FIRE) in conjunction with low- and high-m/z quadrupole isolation and collisionally activated dissociation (CAD) provides new insights into the NECD mechanism. Additionally, activation of the intact complex in either the electrospray droplet or the gas phase produced c-type fragment ions. Similar to the previously reported results on cytochrome c, these fragment ions form near residues known to interact with iron atoms in solution. By mapping the location of backbone cleavages associated with c-type ions onto the crystal structure, we are able to characterize two distinct iron binding channels that facilitate iron ion transport into the core of the complex. The resulting pathways are in good agreement with previously reported results for iron binding sites in mammalian ferritin.
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Project description:When ferritin is reconstituted from Fe and apoferritin in vitro in the presence of Pi, the product obtained differs both from native ferritin and from ferritin reconstituted in the absence of Pi. When the latter is incubated with Pi the product resembles native ferritin with respect both to the pattern of Pi incorporated per molecule or per Fe atom and to the ease of release of this Pi relative to Fe release. It is concluded that much of the Pi of native ferritin is adsorbed on surfaces of ferritin iron-core crystallites. The results also suggest that Pi is not present at the intracellular site of Fe incorporation into ferritin, but is added after Fe.
| S-EPMC1183959 | biostudies-other
Project description:Horse spleen ferritin was found to bind aluminium poorly after equilibrium dialysis with buffered aluminium citrate solutions. Not more than 10 aluminium atoms/ferritin molecule were bound from a 25 microM-aluminium solution, pH 7.4, and the degree of binding was dependent on the method used to prepare the aluminium citrate solution. Up to 120 aluminium atoms/molecule were bound when ferritin iron cores were reconstituted by the addition of 3000 Fe atoms to apoferritin in the presence of aluminium citrate. Comparison of previously published binding constants of ferritin and citrate for aluminium suggests that, in the cell, the prevalence of small ligands effectively prevents the association of large amounts of aluminium with ferritin.
| S-EPMC1133195 | biostudies-other
Project description:The title compound, [Fe(C(12)H(8)N(2))(3)](3)[FeW(12)O(40)]·2H(2)O, was prepared under hydro-thermal conditions. The discrete Keggin-type [FeW(12)O(40)](6-) heteropolyoxoanion has threefold symmetry, with the Fe(II) atom located on the threefold rotation axis. The central FeO(4) tetra-hedron in the anion shares its O atoms with four W(3)O(13) trinuclear units, each of which is made up of three edge-shared WO(6) octa-hedral units. The Fe(II) atom in the complex cation, viz [Fe(phen)(3)](2+) (phen is 1,10-phen-anthroline), shows a slightly distorted octa-hedral geometry defined by six N atoms from three phen ligands. The polyoxoanions pack together with the cations, with the disordered water mol-ecules located in voids; the site occupancy factor for each water O atom is 0.33.
| S-EPMC2961299 | biostudies-literature
Project description:Transition-metal-catalyzed alkene hydrosilylation is one of the most important homogeneous catalytic reactions, and the development of methods that use base metals, especially iron, as catalysts for this transformation is a growing area of research. However, the limited number of ligand scaffolds applicable for base-metal-catalyzed alkene hydrosilylation has seriously hindered advances in this area. Herein, we report the use of 1,10-phenanthroline ligands in base-metal catalysts for alkene hydrosilylation. In particular, iron catalysts with 2,9-diaryl-1,10-phenanthroline ligands exhibit unexpected reactivity and selectivity for hydrosilylation of alkenes, including unique benzylic selectivity with internal alkenes, Markovnikov selectivity with terminal styrenes and 1,3-dienes, and excellent activity toward aliphatic terminal alkenes. According to the mechanistic studies, the unusual benzylic selectivity of this hydrosilylation initiates from ?-? interaction between the phenyl of the alkene and the phenanthroline of the ligand. This ligand scaffold and its unique catalytic model will open possibilities for base-metal-catalyzed hydrosilylation reactions.
| S-EPMC5768772 | biostudies-literature
Project description:Ferritin was purified from chicken liver by two different methods: gel filtration on controlled-pore glass beads, and immunoaffinity chromatography employing a chicken ferritin-specific monoclonal antibody that did not cross-react with horse spleen ferritin. This antibody recognizes intact ferritin and an oligomeric 240 kDa form of the molecule after protein transfer to nitrocellulose, but not the 22 kDa chicken ferritin subunit. Chicken liver ferritin purified by these methods exhibited reduced migration on non-denaturing polyacrylamide gels compared with horse spleen ferritin. These results were consistent with the difference in calculated isoelectric points of chicken and horse ferritin subunits. By two-dimensional gel electrophoresis, chicken ferritin 22 kDa subunits exhibited isoelectric points from 6.1 to 6.6 whereas horse spleen ferritin subunits exhibited isoelectric points of 5.8-6.3. The 240 kDa form of the chicken ferritin molecule had an isoelectric point of 6.6 whereas the 210 kDa form of the horse ferritin molecule had isoelectric points of 5.1 and 4.9. Intact chicken liver ferritin particles were 13.4 +/- 0.8 nm (controlled-pore glass-purified) and 12.5 +/- 0.9 nm (affinity-purified) in diameter when viewed by electron microscopy. Horse spleen ferritin consisted of slightly smaller particles with an average diameter of 11.0 +/- 0.7 nm. However, ferritin from chicken liver and horse spleen co-migrated with an apparent molecular mass of 470 kDa when analysed by Sepharose 4B gel filtration chromatography. These results indicate that, consistent with results from other published purification methods, the chicken ferritin purified by the methods reported here exhibits both structural similarities to, and differences from, horse spleen ferritin.
| S-EPMC1138378 | biostudies-other
Project description:1. Ferritin was isolated from human and horse spleen and liver, and apoferritin prepared therefrom. 2. The electrophoretic mobilities of the four apoferritins were determined on polyacrylamide gels and on cellulose acetate strips, and all found to be equal. 3. Homologous ferritins share reactions of identity in immunodiffusion experiments, whereas heterologous ferritins show only partial identity. 4. The subunit molecular weight of each of the apoferritins was determined by polyacrylamide-gel electrophoresis in sodium dodecyl sulphate and by chromatography on agarose columns in 6m-guanidine-HCl. A value of approx. 18500 was found in all cases. The proteins all had sedimentation coefficients of 17-18S. It thus seems that they have identical quaternary structures. 5. The amino acid compositions of the proteins revealed distinct differences both between organs and between species. This was confirmed by analysis of the tryptic peptide patterns, where it was found that about one-third of the peptides were common to the four proteins and the other two-thirds varied from protein to protein. 6. It is concluded that the apoferritins present in the liver and spleen of human and horse are both organ- and species-specific. 7. The apoferritin isolated from the liver of a patient with idiopathic haemochromatosis was identical with normal human liver apoferritin by the criteria described above.
| S-EPMC1177438 | biostudies-other
Project description:Single crystals of the title heterometallic compound, [Fe(C(12)H(8)N(2))(3)][Cr(NCS)(4)(C(12)H(8)N(2))](2)·3CH(3)CN·H(2)O or [Fe(Cphen)(3)][Cr(NCS)(4)(phen)](2)·3CH(3)CN·H(2)O, were pre-pared using the one-pot open-air reaction of iron powder, Reineckes salt and 1,10-phenanthroline (phen) in acetonitrile. The asymetric unit consists of an [Fe(phen)(3)](2+) cation, two [Cr(phen)(NCS)(4)](-) anions, three acetonitrile solvent mol-ecules and a water mol-ecule. The Fe and Cr atoms both show a slightly distorted octa-hedral FeN(6) and CrN(6) coordination geometry with adjacent angles in the range 79.67?(12)-95.21?(12)°. No classical hydrogen bonding involving the water molecule is observed.
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