scholarly journals Ferritin iron uptake and release. Structure–function relationships

1974 ◽  
Vol 143 (2) ◽  
pp. 445-451 ◽  
Author(s):  
Pauline M. Harrison ◽  
Terence G. Hoy ◽  
Ian G. Macara ◽  
Richard J. Hoare
Keyword(s):  
Structure Function ◽  
Iron Uptake ◽  
Iron Oxidation ◽  
Direct Interaction ◽  
Experimental Results ◽  
The Other ◽  
Iron Core ◽  
Oxidation Reduction ◽  
Ferritin Iron ◽  
Uptake And Release

Iron uptake and release by ferritin molecules of different iron contents show similar profiles. These are discussed in relation to the structure of the ferritin molecule. Two models of iron uptake and release are considered. One involves iron oxidation–reduction sites on the protein. The other allows direct interaction of reagents with the iron-core crystallites. It is concluded that the second model accounts better for the experimental results presented now and in previous publications.

scholarly journals Defining the roles of the threefold channels in iron uptake, iron oxidation and iron-core formation in ferritin: a study aided by site-directed mutagenesis

1993 ◽  
Vol 296 (3) ◽  
pp. 721-728 ◽  
Author(s):  
A Treffry ◽  
E R Bauminger ◽  
D Hechel ◽  
N W Hodson ◽  
I Nowik ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Iron Oxidation ◽  
Site Directed Mutagenesis ◽  
Iron Core ◽  
Directed Mutagenesis ◽  
Difference Spectroscopy ◽  
Iron Storage ◽  
Ferritin Iron ◽  
Iron Storage Protein

This paper aims to define the role of the threefold intersubunit channels in iron uptake and sequestration processes in the iron-storage protein, ferritin. Iron uptake, measured as loss of availability of Fe(II) to ferrozine (due to oxidation), has been studied in recombinant human H-chain ferritins bearing amino acid substitutions in the threefold channels or ferroxidase centres. Similar measurements with recombinant horse L-chain ferritin are compared. It is concluded that significant Fe(II) oxidation occurs only at the H-chain ferroxidase centres and not in the threefold channels, although this route is used by Fe(II) for entry. Investigations by Mössbauer and u.v.-difference spectroscopy show that part of the iron oxidized by H-chain ferritin returns to the threefold channels as Fe(III). This monomeric Fe(III) can be displaced by addition of Tb(III). Fe(III) also moves into the cavity for formation of the iron-core mineral, ferrihydrite. Iron incorporated into ferrihydrite becomes kinetically inert.

scholarly journals μ-1,2-Peroxobridged di-iron(III) dimer formation in human H-chain ferritin

2002 ◽  
Vol 364 (1) ◽  
pp. 57-63 ◽  
Author(s):  
Fadi BOU-ABDALLAH ◽  
Georgia C. PAPAEFTHYMIOU ◽  
Danielle M. SCHESWOHL ◽  
Sean D. STANGA ◽  
Paolo AROSIO ◽  
...  
Keyword(s):  
Iron Oxidation ◽  
Iron Core ◽  
Intermediate Species ◽  
Direct Oxidation ◽  
Dimer Formation ◽  
Complex Species ◽  
Ferritin Iron ◽  
Human Ferritin ◽  
Mössbauer Parameters ◽  
Almost All

Biomineralization of the ferritin iron core involves a complex series of events in which H2O2 is produced during iron oxidation by O2 at a dinuclear centre, the ‘ferroxidase site’, located on the H-subunit of mammalian proteins. Rapid-freeze quench Mössbauer spectroscopy was used to probe the early events of iron oxidation and mineralization in recombinant human ferritin containing 24 H-subunits. The spectra reveal that a μ-1,2-peroxodiFe(III) intermediate (species P) with Mössbauer parameters δ (isomer shift) = 0.58mm/s and ΔEQ (quadrupole splitting) = 1.07mm/s at 4.2K is formed within 50ms of mixing Fe(II) with the apoprotein. This intermediate accounts for almost all of the iron in the sample at 160ms. It subsequently decays within 10s to form a μ-oxodiFe(III)—protein complex (species D), which partially vacates the ferroxidase sites of the protein to generate Fe(III) clusters (species C) at a reaction time of 10min. The intermediate peroxodiFe(III) complex does not decay under O2-limiting conditions, an observation suggesting inhibition of decay by unreacted Fe(II), or a possible role for O2 in ferritin biomineralization in addition to that of direct oxidation of iron(II).

scholarly journals Ferritin iron uptake and release in the presence of metals and metalloproteins: Chemical implications in the brain

2013 ◽  
Vol 257 (19-20) ◽  
pp. 2752-2764 ◽  
Author(s):  
Fernando Carmona ◽  
Òscar Palacios ◽  
Natividad Gálvez ◽  
Rafael Cuesta ◽  
Sílvia Atrian ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Ferritin Iron ◽  
The Brain ◽  
Uptake And Release

scholarly journals Mutational analysis of the channel and loop sequences of human ferritin H-chain

1989 ◽  
Vol 264 (2) ◽  
pp. 381-388 ◽  
Author(s):  
S Levi ◽  
A Luzzago ◽  
F Franceschinelli ◽  
P Santambrogio ◽  
G Cesareni ◽  
...  
Keyword(s):  
Amino Acid ◽  
Iron Uptake ◽  
Iron Oxidation ◽  
Single Amino Acid ◽  
Iron Core ◽  
Amino Acid Residues ◽  
Terminal Sequence ◽  
Loop Sequence ◽  
Human Ferritin ◽  
Ferritin H

Human ferritin H-chain mutants were obtained by engineering the recombinant protein expressed by Escherichia coli. The mutagenesis were directed to the C-terminal sequence forming the hydrophobic channel, to the hydrophilic channel and to the loop sequence. The mutants were analysed for extent of expression, for stability, for capacity to incorporate iron and for kinetics of iron uptake and iron oxidation. Of the 22 mutants analysed only two with deletions of single residues in the loop sequence and one with deletion of the last 28 amino acid residues did not assemble into ferritin-like proteins. The other mutants assembled correctly and showed similar chemical/physical properties to the wild-type; they included duplication of an 18-amino acid-residue stretch, deletion of the last 22 and the last seven residues and various mutations of single amino acid residues. Two mutants with extensive alteration in the C-terminal sequence had a diminished thermostability associated with incapability to incorporate iron though they still catalysed iron oxidation. The mutants with alterations of the sequence around the hydrophilic channel showed diminished iron uptake and oxidation kinetics, together with a slightly larger apparent molecular size. The results indicate (i) that two of the sequences are important for ferritin assembly/stability, (ii) that the presence of the hydrophobic channel is essential for formation of the iron core and (iii) that the sites of iron interaction and the path of iron penetration into ferritin remain unidentified.

scholarly journals Uptake and release of ferritin iron. Surface effects and exchange within the crystalline core

1974 ◽  
Vol 139 (3) ◽  
pp. 603-607 ◽  
Author(s):  
Terence G. Hoy ◽  
Pauline M. Harrison ◽  
Mohammad Shabbir
Keyword(s):  
Surface Area ◽  
Ferric Oxide ◽  
Model System ◽  
Experimental Results ◽  
Iron Surface ◽  
Hydrous Ferric Oxide ◽  
Crystalline Core ◽  
Ferritin Iron ◽  
Cation Sites ◽  
Uptake And Release

The uptake and subsequent release of iron by apoferritin and ferritin was studied by using labelled iron (59Fe). The experimental results are consistent with predictions arising from a model system developed in the interpretation of previous experiments. In this model, uptake and release of ferritin iron is controlled by the available surface area of the small crystalline particles of hydrous ferric oxide found within the ferritin molecule. Evidence is also presented for the exchange of Fe3+ ions among the various cation sites within these crystallites.

THE FORMATION, STRUCTURE AND DISSOLUTION OF THE FERRITIN IRON CORE STUDIED BY X-RAY ABSORPTION SPECTROSCOPY

1986 ◽  
Vol 47 (C8) ◽  
pp. C8-1155-C8-1157
Author(s):  
E. C. THEIL ◽  
D. E. SAYERS ◽  
C. Y. YANG ◽  
A. FONTAINE ◽  
E. DARTYGE
Keyword(s):  
Absorption Spectroscopy ◽  
Iron Core ◽  
X Ray ◽  
Ferritin Iron ◽  
X Ray Absorption

The Influence of Water Regime on the Performance of Aquatic Plants

1994 ◽  
Vol 29 (4) ◽  
pp. 127-132 ◽  
Author(s):  
Naomi Rea ◽  
George G. Ganf
Keyword(s):  
Deep Water ◽  
Aquatic Plants ◽  
Water Regime ◽  
Optimal Performance ◽  
Experimental Results ◽  
The Other ◽  
Full Potential ◽  
Influence Of Water ◽  
Emergent Species

Experimental results demonstrate bow small differences in depth and water regime have a significant affect on the accumulation and allocation of nutrients and biomass. Because the performance of aquatic plants depends on these factors, an understanding of their influence is essential to ensure that systems function at their full potential. The responses differed for two emergent species, indicating that within this morphological category, optimal performance will fall at different locations across a depth or water regime gradient. The performance of one species was unaffected by growth in mixture, whereas the other performed better in deep water and worse in shallow.

Mining discriminative patches for script identification in natural scene images

2021 ◽  
Vol 40 (1) ◽  
pp. 551-563
Author(s):  
Liqiong Lu ◽  
Dong Wu ◽  
Ziwei Tang ◽  
Yaohua Yi ◽  
Faliang Huang
Keyword(s):  
Neural Networks ◽  
Experimental Results ◽  
The Other ◽  
Natural Scene ◽  
Fixed Size ◽  
Script Identification ◽  
Aspect Ratios ◽  
Novel Approach ◽  
Public Datasets ◽  
Natural Scene Images

This paper focuses on script identification in natural scene images. Traditional CNNs (Convolution Neural Networks) cannot solve this problem perfectly for two reasons: one is the arbitrary aspect ratios of scene images which bring much difficulty to traditional CNNs with a fixed size image as the input. And the other is that some scripts with minor differences are easily confused because they share a subset of characters with the same shapes. We propose a novel approach combing Score CNN, Attention CNN and patches. Attention CNN is utilized to determine whether a patch is a discriminative patch and calculate the contribution weight of the discriminative patch to script identification of the whole image. Score CNN uses a discriminative patch as input and predict the score of each script type. Firstly patches with the same size are extracted from the scene images. Secondly these patches are used as inputs to Score CNN and Attention CNN to train two patch-level classifiers. Finally, the results of multiple discriminative patches extracted from the same image via the above two classifiers are fused to obtain the script type of this image. Using patches with the same size as inputs to CNN can avoid the problems caused by arbitrary aspect ratios of scene images. The trained classifiers can mine discriminative patches to accurately identify some confusing scripts. The experimental results show the good performance of our approach on four public datasets.

scholarly journals DV-DVFS: merging data variety and DVFS technique to manage the energy consumption of big data processing

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hossein Ahmadvand ◽  
Fouzhan Foroutan ◽  
Mahmood Fathy
Keyword(s):  
Big Data ◽  
Energy Consumption ◽  
Processing Time ◽  
Experimental Results ◽  
The Other ◽  
Data Sets ◽  
Multiple Sources ◽  
Evaluation Phase ◽  
Dynamic Voltage ◽  
Processing Resources

AbstractData variety is one of the most important features of Big Data. Data variety is the result of aggregating data from multiple sources and uneven distribution of data. This feature of Big Data causes high variation in the consumption of processing resources such as CPU consumption. This issue has been overlooked in previous works. To overcome the mentioned problem, in the present work, we used Dynamic Voltage and Frequency Scaling (DVFS) to reduce the energy consumption of computation. To this goal, we consider two types of deadlines as our constraint. Before applying the DVFS technique to computer nodes, we estimate the processing time and the frequency needed to meet the deadline. In the evaluation phase, we have used a set of data sets and applications. The experimental results show that our proposed approach surpasses the other scenarios in processing real datasets. Based on the experimental results in this paper, DV-DVFS can achieve up to 15% improvement in energy consumption.

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