scholarly journals Ferritin exhibits Michaelis–Menten behavior with oxygen but not with iron during iron oxidation and core mineralization

Metallomics ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 774-783 ◽  
Author(s):  
Fadi Bou-Abdallah ◽  
Nicholas Flint ◽  
Tyler Wilkinson ◽  
Samantha Salim ◽  
Ayush Kumar Srivastava ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Iron Oxidation ◽  
Iron Saturation ◽  
Saturation Kinetics

Iron uptake into mammalian ferritins reveals oxygen (but not iron) saturation kinetics and physiologically relevant Km,O2 values.

Dps biomineralizing proteins: multifunctional architects of nature

2012 ◽  
Vol 445 (3) ◽  
pp. 297-311 ◽  
Author(s):  
Kornelius Zeth
Keyword(s):  
Iron Uptake ◽  
Iron Oxidation ◽  
Hollow Spheres ◽  
Cell Communication ◽  
Memory Storage ◽  
Oxygen Species ◽  
Inner Surface ◽  
Technical Production ◽  
Catalytic Functions ◽  
Ros Reactive Oxygen Species

Dps proteins are the structural relatives of bacterioferritins and ferritins ubiquitously present in the bacterial and archaeal kingdoms. The ball-shaped enzymes play important roles in the detoxification of ROS (reactive oxygen species), in iron scavenging to prevent Fenton reactions and in the mechanical protection of DNA. Detoxification of ROS and iron chaperoning represent the most archetypical functions of dodecameric Dps enzymes. Recent crystallographic studies of these dodecameric complexes have unravelled species-dependent mechanisms of iron uptake into the hollow spheres. Subsequent functions in iron oxidation at ferroxidase centres are highly conserved among bacteria. Final nucleation of iron as iron oxide nanoparticles has been demonstrated to originate at acidic residues located on the inner surface. Some Dps enzymes are also implicated in newly observed catalytic functions related to the formation of molecules playing roles in bacterium–host cell communication. Most recently, Dps complexes are attracting attention in semiconductor science as biomimetic tools for the technical production of the smallest metal-based quantum nanodots used in nanotechnological approaches, such as memory storage or solar cell development.

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.

The in Vivo Plasma Clearance of Iron from Transferrins of Low and High Iron Saturation

1970 ◽  
Vol 38 (6) ◽  
pp. 783-793 ◽  
Author(s):  
R. S. Lane ◽  
C. A. Finch
Keyword(s):  
Iron Uptake ◽  
Plasma Clearance ◽  
High Plasma ◽  
Clearance Time ◽  
Plasma Iron ◽  
High Iron ◽  
Iron Saturation ◽  
In Vivo Release ◽  
Iron Pool

1. The rate of in vivo release of iron from plasma transferrin samples at low and high saturation was measured simultaneously in fifteen subjects with differing amounts of body iron and different rates of erythropoiesis. Iron atoms bound to transferrin at low and high plasma iron saturation were identified by using tracer labels 55Fe and 59Fe respectively. Results were expressed as the plasma 55Fe and 59Fe half-clearance time. 2. Plasma iron clearance times ranged from 15·6 to 350 min, reflecting the different amounts of available iron and marrow requirements of the patients studied. The simultaneous rates of 55Fe and 59Fe clearance from the plasma were the same in thirteen patients. Clearances in two subjects showed differences between the two isotopes, but clearances of the identical paired isotopes in two other subjects showed no difference. 3. These results confirm earlier findings of homogeneity in the plasma iron pool, extending the observations to include varying per cent saturation of transferrin and varying rates of iron uptake.

scholarly journals Effect of Iron Saturation of Transferrin on Hepatic Iron Uptake: An in Vitro Study

1977 ◽  
Vol 72 (1) ◽  
pp. 129-131 ◽  
Author(s):  
A.P. Zimelman ◽  
H.J. Zimmerman ◽  
R. McLean ◽  
L.R. Weintraub
Keyword(s):  
Iron Uptake ◽  
In Vitro Study ◽  
Vitro Study ◽  
Hepatic Iron ◽  
Iron Saturation

Regulation of Expression of the PetI Operon Involved in Iron Oxidation in the Biomining Bacterium Acidithiobacillus Ferrooxidans

2009 ◽  
Vol 71-73 ◽  
pp. 199-202 ◽  
Author(s):  
C. Lefimil ◽  
Hector Osorio ◽  
Raquel Quatrini ◽  
David S. Holmes ◽  
Eugenia Jedlicki
Keyword(s):  
Binding Sites ◽  
Acidithiobacillus Ferrooxidans ◽  
Iron Uptake ◽  
Anaerobic Metabolism ◽  
Reverse Flow ◽  
Iron Oxidation ◽  
Regulation Of Expression ◽  
Dna Binding Sites ◽  
Gain Energy ◽  
Electron Transport Proteins

Acidithiobacillus ferrooxidans is an acidophilic, chemolithotrophic bacterium that can gain energy and electrons by the oxidation of iron. PetI is an operon that encodes electron transport proteins involved in the reverse flow of electrons from iron to the NAD complex during iron oxidation. Although a substantial body of evidence describes the components and pathways for iron oxidation, little is known about their regulation. It is proposed that environmental iron concentrations and oxygen levels could influence the ability of A. ferrooxidans to oxidize iron as an energy source. We report initial investigators into the possibility that the expression of the PetI operon is regulated, inter alia, by the master transcription factor controlling iron uptake and homeostasis (Fur) and anaerobic metabolism (FNR). Potential DNA binding sites (boxes) for both regulators were predicted in the region of the PetI operon promoter and the binding of Fur to its cognate box was demonstrated experimentally. This represents the first attempt to unravel the mechanisms involved in the regulation of iron oxidation.

Transferrin and iron uptake by rat hepatocytes in culture

1984 ◽  
Vol 246 (1) ◽  
pp. G26-G33 ◽  
Author(s):  
M. A. Page ◽  
E. Baker ◽  
E. H. Morgan
Keyword(s):  
Iron Uptake ◽  
Rat Hepatocytes ◽  
Molar Ratio ◽  
Adult Rat ◽  
Iron Saturation ◽  
Primary Monolayer Culture ◽  
Primary Monolayer ◽  
Diferric Transferrin ◽  
Transferrin Uptake ◽  
Linear Manner

Hepatic iron and transferrin metabolism was studied using rat transferrin doubly labeled with 59Fe and 125I and adult rat hepatocytes in primary monolayer culture. Iron uptake was linear for 48 h while transferrin uptake was biphasic. Total transferrin and iron uptake increased in a linear manner as the transferrin concentration was raised up to at least 130 microM. This indicates that transferrin and iron are taken up primarily by nonspecific processes, possibly by endocytosis (absorptive or fluid) and by the action of iron chelators. However, some evidence indicated the presence of receptors for diferric transferrin on hepatocytes: the molar ratio of iron to transferrin accumulation increased with incubation time, transferrin and iron uptake was proportional to the iron saturation of the transferrin, apotransferrin displaced bound apotransferrin but had no effect on the binding of diferric transferrin, and the molar ratio of iron to transferrin uptake decreased with increasing transferrin concentrations.

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 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.

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