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BBA - General Subjects (v.1800, #8)
The Ferritin-like superfamily: Evolution of the biological iron storeman from a rubrerythrin-like ancestor by Simon C. Andrews (pp. 691-705).
The Ferritins are part of the extensive ‘Ferritin-like superfamily’ which have diverse functions but are linked by the presence of a common four-helical bundle domain. The role performed by Ferritins as the cellular repository of excess iron is unique. In many ways Ferritins act as tiny organelles in their ability to secrete iron away from the delicate machinery of the cell, and then to release it again in a controlled fashion avoiding toxicity. The Ferritins are ancient proteins, being common in all three domains of life. This ubiquity reflects the key contribution that Ferritins provide in achieving iron homeostasis.This review compares the features of the different Ferritins and considers how they, and other members of the Ferritin-like superfamily, have evolved. It also considers relevant features of the eleven other known families within the Ferritin-like superfamily, particularly the highly diverse rubrerythrins.The Ferritins have travelled a considerable evolutionary journey, being derived from far more simplistic rubrerythrin-like molecules which play roles in defence against toxic oxygen species. The forces of evolution have moulded such molecules into three distinct types of iron storing (or detoxifying) protein: the classical and universal 24-meric ferritins; the haem-containing 24-meric bacterioferritins of prokaryotes; and the prokaryotic 12-meric Dps proteins. These three Ferritin types are similar, but also possess unique properties that distinguish them and enable then to achieve their specific physiological purposes.A wide range of biological functions have evolved from a relatively simple structural unit.
Keywords: Rubrerythrin; Erythrin; 4-helix bundle; Dps; Ferritin; Bacterioferritin
X-ray structures of ferritins and related proteins by Robert R. Crichton; Jean-Paul Declercq (pp. 706-718).
Ferritins are members of a much larger superfamily of proteins, which are characterised by a structural motif consisting of a bundle of four parallel and anti-parallel α helices. The ferritin superfamily itself is widely distributed across all three living kingdoms, in both aerobic and anaerobic organisms, and a considerable number of X-ray structures are available, some at extremely high resolution. We describe first of all the subunit structure of mammalian H and L chain ferritins and then discuss intersubunit interactions in the 24-subunit quaternary structure of these ferritins. Bacteria contain two types of ferritins, FTNs, which like mammalian ferritins do not contain haem, and the haem-containing BFRs. The characteristic carboxylate-bridged di-iron ferroxidase sites of H chain ferritins, FTNs and BFRs are compared, as are the potential entry sites for iron and the ‘nucleation’ site of L chain ferritins. Finally we discuss the three-dimensional structures of the 12-subunit bacterial Dps (DNA-binding protein from starved cells) proteins as well as their intersubunit di-iron ferroxidase site.
Keywords: Iron; Ferritin; Iron storage; Protein structure; X-ray structures; Bacterioferritin; Dps protein; Rubrerythrin
The iron redox and hydrolysis chemistry of the ferritins by Fadi Bou-Abdallah (pp. 719-731).
Ferritins are ubiquitous and well-characterized iron storage and detoxification proteins. In bacteria and plants, ferritins are homopolymers composed of H-type subunits, while in vertebrates, they typically consist of 24 similar subunits of two types, H and L. The H-subunit is responsible for the rapid oxidation of Fe(II) to Fe(III) at a dinuclear center, whereas the L-subunit appears to help iron clearance from the ferroxidase center of the H-subunit and support iron nucleation and mineralization.Despite their overall similar structures, ferritins from different origins markedly differ in their iron binding, oxidation, detoxification, and mineralization properties. This chapter provides a brief overview of the structure and function of ferritin, reviews our current knowledge of the process of iron uptake and mineral core formation, and highlights the similarities and differences of the iron oxidation and hydrolysis chemistry in a number of ferritins including those from archaea, bacteria, amphibians, and animals.Prokaryotic ferritins and ferritin-like proteins (Dps) appear to preferentially use H2O2 over O2 as the iron oxidant during ferritin core formation. While the product of iron oxidation at the ferroxidase centers of these and other ferritins is labile and is retained inside the protein cavity, the iron complex in the di-iron cofactor proteins is stable and remains at the catalytic site. Differences in the identity and affinity of the ferroxidase center ligands to iron have been suggested to influence the distinct reaction pathways in ferritins and the di-iron cofactor enzymes.The ferritin 3-fold channels are shown to be flexible structures that allow the entry and exit of different ions and molecules through the protein shell. The H- and L-subunits are shown to have complementary roles in iron oxidation and mineralization, and hydrogen peroxide appears to be a by-product of oxygen reduction at the FC of most ferritins. The di-iron(III) complex at the FC of some ferritins acts as a stable cofactor during iron oxidation rather than a catalytic center where Fe(II) is oxidized at the FC followed by its translocation to the protein cavity.
Keywords: Abbreviations; Dps; D; NA binding; p; roteins from; s; tarved cell; HuHF and HuLF; human H-chain and L-chain ferritins; MtF; human mitochondrial ferritin; HoSF; horse spleen ferritin; BfMF; bullfrog M-chain ferritin; EcBFR and EcFtnA; heme- and nonheme-containing; Escherichia coli; ferritins; AvBF and DdBF; Azotobacter vinelandii; and; Desulfovibrio desulfuricans; bacterioferritins; PfFtn and AfFtn; Pyrococcus furiosus; and; Archaeoglobus fulgidus; archaeal ferritins; ITC; isothermal titration calorimetry; EXAFS; extended X-ray absorption fine structure; EPR; electron paramagnetic resonance spectroscopy; FC; ferroxidase centerIron oxidation; Mineral core formation; Iron detoxification; Ferritin channel; Ferroxidase center; Di-iron peroxo complex; Di-iron oxo complex; Heteropolymer; H- and L-subunit
Iron core mineralisation in prokaryotic ferritins by Nick E. Le Brun; Allister Crow; Michael E.P. Murphy; A. Grant Mauk; Geoffrey R. Moore (pp. 732-744).
To satisfy their requirement for iron while at the same time countering the toxicity of this highly reactive metal ion, prokaryotes have evolved proteins belonging to two distinct sub-families of the ferritin family: the bacterioferritins (BFRs) and the bacterial ferritins (Ftns). Recently, Ftn homologues have also been identified and characterised in archaeon species. All of these prokaryotic ferritins function by solubilising and storing large amounts of iron in the form of a safe but bio-available mineral.The mechanism(s) by which the iron mineral is formed by these proteins is the subject of much current interest. Here we review the available information on these proteins, with particular emphasis on significant advances resulting from recent structural, spectroscopic and kinetic studies.Current understanding indicates that at least two distinct mechanisms are in operation in prokaryotic ferritins. In one, the ferroxidase centre acts as a true catalytic centre in driving Fe2+ oxidation in the cavity; in the other, the centre acts as a gated iron pore by oxidising Fe2+ and transferring the resulting Fe3+ into the central cavity.The prokaryotic ferritins exhibit a wide variation in mechanisms of iron core mineralisation. The basis of these differences lies, at least in part, in structural differences at and around the catalytic centre. However, it appears that more subtle differences must also be important in controlling the iron chemistry of these remarkable proteins.
Keywords: Bacterioferritin; Ftn; Iron; Diiron centre; Ferroxidase; Mineralisation; Heme
Oxido-reduction is not the only mechanism allowing ions to traverse the ferritin protein shell by Richard K. Watt; Robert J. Hilton; D. Matthew Graff (pp. 745-759).
Most models for ferritin iron release are based on reduction and chelation of iron. However, newer models showing direct Fe(III) chelation from ferritin have been proposed. Fe(III) chelation reactions are facilitated by gated pores that regulate the opening and closing of the channels.Results suggest that iron core reduction releases hydroxide and phosphate ions that exit the ferritin interior to compensate for the negative charge of the incoming electrons. Additionally, chloride ions are pumped into ferritin during the reduction process as part of a charge balance reaction. The mechanism of anion import or export is not known but is a natural process because phosphate is a native component of the iron mineral core and non-native anions have been incorporated into ferritin in vitro. Anion transfer across the ferritin protein shell conflicts with spin probe studies showing that anions are not easily incorporated into ferritin. To accommodate both of these observations, ferritin must possess a mechanism that selects specific anions for transport into or out of ferritin. Recently, a gated pore mechanism to open the 3-fold channels was proposed and might explain how anions and chelators can penetrate the protein shell for binding or for direct chelation of iron.These proposed mechanisms are used to evaluate three in vivo iron release models based on (1) equilibrium between ferritin iron and cytosolic iron, (2) iron release by degradation of ferritin in the lysosome, and (3) metallo-chaperone mediated iron release from ferritin.
Keywords: Abbreviations; DFO; Desferal, desferoxamine, desferrioxamine, desferrioxamine B; bipy; bipyridyl; PB; Prussian blue; FAC; Ferric ammonium citrate; ROS; reactive oxygen species; c-acon; aconitase; IRP-1; iron-responsive protein -1; EPR; electron paramagnetic resonance; LIP; labile iron poolLong-range electron transfer; Oxido-reduction; Anion transport; Ferritin iron release; Gated pores; Bacterioferritin
Serum ferritin: Past, present and future by Wei Wang; Mary Ann Knovich; Lan G. Coffman; Frank M. Torti; Suzy V. Torti (pp. 760-769).
Serum ferritin was discovered in the 1930s, and was developed as a clinical test in the 1970s. Many diseases are associated with iron overload or iron deficiency. Serum ferritin is widely used in diagnosing and monitoring these diseases.In this chapter, we discuss the role of serum ferritin in physiological and pathological processes and its use as a clinical tool.Although many aspects of the fundamental biology of serum ferritin remain surprisingly unclear, a growing number of roles have been attributed to extracellular ferritin, including newly described roles in iron delivery, angiogenesis, inflammation, immunity, signaling and cancer.Serum ferritin remains a clinically useful tool. Further studies on the biology of this protein may provide new biological insights.
Keywords: Ferritin; Iron; Iron store; Ferritin receptor; Inflammation; Cancer
Could a dysfunction of ferritin be a determinant factor in the aetiology of some neurodegenerative diseases? by Carmen Quintana; Gutierrez Lucía Gutiérrez (pp. 770-782).
The concentration of iron in the brain increases with aging. Furthermore, it has also been observed that patients suffering from neurological diseases (e.g. Parkinson, Alzheimer…) accumulate iron in the brain regions affected by the disease. Nevertheless, it is still not clear whether this accumulation is the initial cause or a secondary consequence of the disease. Free iron excess may be an oxidative stress source causing cell damage if it is not correctly stored in ferritin cores as a ferric iron oxide redox-inert form.Both, the composition of ferritin cores and their location at subcellular level have been studied using analytical transmission electron microscopy in brain tissues from progressive supranuclear palsy (PSP) and Alzheimer disease (AD) patients.Ferritin has been mainly found in oligodendrocytes and in dystrophic myelinated axons from the neuropili in AD. In relation to the biomineralization of iron inside the ferritin shell, several different crystalline structures have been observed in the study of physiological and pathological ferritin. Two cubic mixed ferric–ferrous iron oxides are the major components of pathological ferritins whereas ferrihydrite, a hexagonal ferric iron oxide, is the major component of physiological ferritin. We hypothesize a dysfunction of ferritin in its ferroxidase activity.The different mineralization of iron inside ferritin may be related to oxidative stress in olygodendrocites, which could affect myelination processes with the consequent perturbation of information transference.
Keywords: Abbreviations; Aβ; Amyloid beta peptide; AD; Alzheimer's disease; ATEM; Analytical transmission electron microscopy; CAT; Computed axial tomography; ED; Electron diffraction; EELS; Electron energy loss spectrometry; END; Electron nanodiffraction; EXAFS; Extended X-ray Absorption Fine Structure; HAADF; High Angle Annular Dark Field; HRTEM; High resolution transmission electron microscopy; MRI; Magnetic resonance imaging; PHF; Paired helical filaments; PET; Positron emission tomography; PSP; Progressive supranuclear palsy; ROI; Regions of interest; SAD; Selected area diffraction; SIMS; Secondary Ion Mass Spectroscopy; SP; Senile (neuritic) plaques; STEM; Scanning Transmission Electron Microscopy; TEM; Transmission electron microscopy; XANES; X-ray Absorption Near Edge Structure; XRD; X-ray diffraction; XRF; X-ray fluorescenceFerritin; Haemosiderin; Analytical electron microscopy; Oligodendrocyte; Alzheimer disease; Dystrophic myelinated axon
Cytosolic and mitochondrial ferritins in the regulation of cellular iron homeostasis and oxidative damage by Paolo Arosio; Sonia Levi (pp. 783-792).
Ferritin structure is designed to maintain large amounts of iron in a compact and bioavailable form in solution. All ferritins induce fast Fe(II) oxidation in a reaction catalyzed by a ferroxidase center that consumes Fe(II) and peroxides, the reagents that produce toxic free radicals in the Fenton reaction, and thus have anti-oxidant effects. Cytosolic ferritins are composed of the H- and L-chains, whose expression are regulated by iron at a post-transcriptional level and by oxidative stress at a transcriptional level. The regulation of mitochondrial ferritin expression is presently unclear.The scope of the review is to update recent progress regarding the role of ferritins in the regulation of cellular iron and in the response to oxidative stress with particular attention paid to the new roles described for cytosolic ferritins, to genetic disorders caused by mutations of the ferritin L-chain, and new findings on mitochondrial ferritin.The new data on the adult conditional knockout (KO) mice for the H-chain and on the hereditary ferritinopathies with mutations that reduce ferritin functionality strongly indicate that the major role of ferritins is to protect from the oxidative damage caused by iron deregulation. In addition, the study of mitochondrial ferritin, which is not iron-regulated, indicates that it participates in the protection against oxidative damage, particularly in cells with high oxidative activity.Ferritins have a central role in the protection against oxidative damage, but they are also involved in non-iron-dependent processes.
Keywords: Ferritin; Oxidative damage; Iron homeostasis; Neurodegeneration; Mitochondria
Nuclear ferritin: A new role for ferritin in cell biology by Ahmed A. Alkhateeb; James R. Connor (pp. 793-797).
Ferritin has been traditionally considered a cytoplasmic iron storage protein. However, several studies over the last two decades have reported the nuclear localization of ferritin, specifically H-ferritin, in developing neurons, hepatocytes, corneal epithelial cells, and some cancer cells. These observations encouraged a new perspective on ferritin beyond iron storage, such as a role in the regulation of iron accessibility to nuclear components, DNA protection from iron-induced oxidative damage, and transcriptional regulation.This review will address the translocation and functional significance of nuclear ferritin in the context of human development and disease.The nuclear translocation of ferritin is a selective energy-dependent process that does not seem to require a consensus nuclear localization signal. It is still unclear what regulates the nuclear import/export of ferritin. Some reports have implicated the phosphorylation and O-glycosylation of the ferritin protein in nuclear transport; others suggested the existence of a specific nuclear chaperone for ferritin. The data argue strongly for nuclear ferritin as a factor in human development and disease. Ferritin can bind and protect DNA from oxidative damage. It also has the potential of playing a regulatory role in transcription.Nuclear ferritin represents a novel new outlook on ferritin functionality beyond its classical role as an iron storage molecule.
Keywords: Ferritin; Nuclear ferritin; Iron storage; DNA protection
The multifaceted capacity of Dps proteins to combat bacterial stress conditions: Detoxification of iron and hydrogen peroxide and DNA binding by Emilia Chiancone; Pierpaolo Ceci (pp. 798-805).
The widely expressed Dps proteins, so named after the DNA-binding properties of the first characterized member of the family in Escherichia coli, are considered major players in the bacterial response to stress.The review describes the distinctive features of the “ferritin-like” ferroxidation reaction, which uses hydrogen peroxide as physiological iron oxidant and therefore permits the concomitant removal of the two reactants that give rise to hydroxyl radicals via Fenton chemistry. It also illustrates the structural elements identified to date that render the interaction of some Dps proteins with DNA possible and outlines briefly the significance of Dps–DNA complex formation and of the Dps interaction with other DNA-binding proteins in relation to the organization of the nucleoid and microbial survival.Understanding in molecular terms the distinctive role of Dps proteins in bacterial resistance to general and specific stress conditions.The state of the art is that the response to oxidative and peroxide-mediated stress is mediated directly by Dps proteins via their ferritin-like activity. In contrast, the response to other stress conditions derives from the concerted interplay of diverse interactions that Dps proteins may establish with DNA and with other DNA-binding proteins.
Keywords: Dps (DNA-binding proteins from starved cells) protein; Ferroxidase activity; Dps–DNA interaction; Protection under oxidative damage condition; Microbial survival; Review
Ferritins and iron storage in plants by Jean-François Briat; Céline Duc; Karl Ravet; Frédéric Gaymard (pp. 806-814).
Iron is essential for both plant productivity and nutritional quality. Improving plant iron content was attempted through genetic engineering of plants overexpressing ferritins. However, both the roles of these proteins in the plant physiology, and the mechanisms involved in the regulation of their expression are largely unknown. Although the structure of ferritins is highly conserved between plants and animals, their cellular localization differ. Furthermore, regulation of ferritin gene expression in response to iron excess occurs at the transcriptional level in plants, in contrast to animals which regulate ferritin expression at the translational level. In this review, our knowledge of the specific features of plant ferritins is presented, at the level of their (i) structure/function relationships, (ii) cellular localization, and (iii) synthesis regulation during development and in response to various environmental cues. A special emphasis is given to their function in plant physiology, in particular concerning their respective roles in iron storage and in protection against oxidative stress. Indeed, the use of reverse genetics in Arabidopsis recently enabled to produce various knock-out ferritin mutants, revealing strong links between these proteins and protection against oxidative stress. In contrast, their putative iron storage function to furnish iron during various development processes is unlikely to be essential. Ferritins, by buffering iron, exert a fine tuning of the quantity of metal required for metabolic purposes, and help plants to cope with adverse situations, the deleterious effects of which would be amplified if no system had evolved to take care of free reactive iron.
Keywords: Iron homeostasis; Oxidative stress; Chloroplast; Vacuole
Phytoferritin and its implications for human health and nutrition by Guanghua Zhao (pp. 815-823).
Plant and animal ferritins stem from a common ancestor, but plant ferritins exhibit various features that are different from those of animal ferritins. Phytoferritin is observed in plastids (e.g., chloroplasts in leaves, amyloplasts in tubers and seeds), whereas animal ferritin is largely found in the cytoplasm. The main difference in structure between plant and animal ferritins is the two specific domains (TP and EP) at the N-terminal sequence of phytoferritin, which endow phytoferritin with specific iron chemistry. As a member of the nonheme iron group of dietary iron sources, phytoferritin consists of 24 subunits that assemble into a spherical shell storing up to ∼2000 Fe3+ in the form of an iron oxyhydroxide-phosphate mineral. This feature is distinct from small molecule nonheme iron existing in cereals, which has poor bioavailability.This review focuses on the relationship between structure and function of phytoferritin and the recent progress in the use of phytoferritin as iron supplement.Phytoferritin, especially from legume seeds, represents a novel alternative dietary iron source.An understanding of the chemistry and biology of phytoferritin, its interaction with iron, and its stability against gastric digestion is beneficial to design diets that will be used for treatment of global iron deficiency.
Keywords: Phytoferritin; EP; Iron oxidative deposition; Association; Iron core; Bioavailability; Iron uptake
Insect ferritins: Typical or atypical? by Daphne Q.D. Pham; Joy J. Winzerling (pp. 824-833).
Insects transmit millions of cases of disease each year, and cost millions of dollars in agricultural losses. The control of insect-borne diseases is vital for numerous developing countries, and the management of agricultural insect pests is a very serious business for developed countries. Control methods should target insect-specific traits in order to avoid non-target effects, especially in mammals. Since insect cells have had a billion years of evolutionary divergence from those of vertebrates, they differ in many ways that might be promising for the insect control field—especially, in iron metabolism because current studies have indicated that significant differences exist between insect and mammalian systems. Insect iron metabolism differs from that of vertebrates in the following respects. Insect ferritins have a heavier mass than mammalian ferritins. Unlike their mammalian counterparts, the insect ferritin subunits are often glycosylated and are synthesized with a signal peptide. The crystal structure of insect ferritin also shows a tetrahedral symmetry consisting of 12 heavy chain and 12 light chain subunits in contrast to that of mammalian ferritin that exhibits an octahedral symmetry made of 24 heavy chain and 24 light chain subunits. Insect ferritins associate primarily with the vacuolar system and serve as iron transporters—quite the opposite of the mammalian ferritins, which are mainly cytoplasmic and serve as iron storage proteins. This review will discuss these differences.
Keywords: Ferritin; Infection; Iron transporter; Insect; Oxidative stress; Secreted
The ferritin superfamily: Supramolecular templates for materials synthesis by Masaki Uchida; Sebyung Kang; Courtney Reichhardt; Kevin Harlen; Trevor Douglas (pp. 834-845).
Members of the ferritin superfamily are multi-subunit cage-like proteins with a hollow interior cavity. These proteins possess three distinct surfaces, i.e. interior and exterior surfaces of the cages and interface between subunits. The interior cavity provides a unique reaction environment in which the interior reaction is separated from the external environment. In biology the cavity is utilized for sequestration of irons and biomineralization as a mechanism to render Fe inert and sequester it from the external environment. Material scientists have been inspired by this system and exploited a range of ferritin superfamily proteins as supramolecular templates to encapsulate nanoparticles and/or as well-defined building blocks for fabrication of higher order assembly. Besides the interior cavity, the exterior surface of the protein cages can be modified without altering the interior characteristics. This allows us to deliver the protein cages to a targeted tissue in vivo or to achieve controlled assembly on a solid substrate to fabricate higher order structures. Furthermore, the interface between subunits is utilized for manipulating chimeric self-assembly of the protein cages and in the generation of symmetry-broken Janus particles. Utilizing these ideas, the ferritin superfamily has been exploited for development of a broad range of materials with applications from biomedicine to electronics.
Keywords: Ferritin; Dps (; D; NA binding; p; rotein from nutrient; s; tarved cells); Nanoparticle; Multifunctionalities; Biomimetic chemistry; Janus particle; Bio-template
Ferritin in the field of nanodevices by Ichiro Yamashita; Kenji Iwahori; Shinya Kumagai (pp. 846-857).
Biomineralization of ferritin core has been extended to the artificial synthesis of homogeneous metal complex nanoparticles (NPs) and semiconductor NPs. The inner cavity of apoferritin is an ideal spatially restricted chemical reaction chamber for NP synthesis. The obtained ferritin (biocomplexes, NP and the surrounding protein shell) has attracted great interest among researchers in the field of nanodevices. Ferritins were delivered onto specific substrate locations in a one-by-one manner or a hexagonally close-packed array through ferritin outer surface interactions. After selective elimination of protein shells from the ferritin, bare NPs were left at the positions where they were delivered. The obtained NPs were used as catalysts for carbon nanotube (CNT) growth and metal induced lateral crystallization (MILC), charge storage nodes of floating gate memory, and nanometer-scale etching masks, which could not be performed by other methods.
Keywords: Ferritin; Biomineralization; Nanodevice; Nanoparticle; Self-organization
The sedimentation properties of ferritins. New insights and analysis of methods of nanoparticle preparation by Carrie A. May; John K. Grady; Thomas M. Laue; Maura Poli; Paolo Arosio; N. Dennis Chasteen (pp. 858-870).
Ferritin exhibits complex behavior in the ultracentrifuge due to variability in iron core size among molecules. A comprehensive study was undertaken to develop procedures for obtaining more uniform cores and assessing their homogeneity.Analytical ultracentrifugation was used to measure the mineral core size distributions obtained by adding iron under high- and low-flux conditions to horse spleen (apoHoSF) and human H-chain (apoHuHF) apoferritins.More uniform core sizes are obtained with the homopolymer human H-chain ferritin than with the heteropolymer horse spleen HoSF protein in which subpopulations of HoSF molecules with varying iron content are observed. A binomial probability distribution of H- and L-subunits among protein shells qualitatively accounts for the observed subpopulations. The addition of Fe2+ to apoHuHF produces iron core particle size diameters from 3.8±0.3 to 6.2±0.3nm. Diameters from 3.4±0.6 to 6.5±0.6nm are obtained with natural HoSF after sucrose gradient fractionation. The change in the sedimentation coefficient as iron accumulates in ferritin suggests that the protein shell contracts ∼10% to a more compact structure, a finding consistent with published electron micrographs. The physicochemical parameters for apoHoSF (15%/85% H/L subunits) are M=484,120g/mol, ν̅=0.735mL/g, s20, w=17.0S and D 20,w=3.21×10−7cm2/s; and for apoHuHF M=506,266g/mol, ν̅=0.724mL/g, s20, w=18.3S and D 20,w=3.18×10−7cm2/s.The methods presented here should prove useful in the synthesis of size controlled nanoparticles of other minerals.
Keywords: Abbreviations; AUC; analytical ultracentrifugation; DTT; dithiothreitol; HoSF; horse spleen ferritin; HuHF; recombinant human H-chain ferritin; MOPS; 3-(N-morpholino)propanesulfonic acid; TEM; transmission electron microscopy; D; diffusion coefficient (cm; 2; /s) under the specific conditions of protein concentration, buffer and temperature; c; concentration (g/cm; 3; ); D; 20,; w; o; diffusion coefficient of infinite dilute protein in pure water at 20; °C (cm; 2; /s); D; 20,; w; diffusion coefficient of the protein at the stated concentration in pure water at 20; °C (cm; 2; /s); d; Stokes diameter (nm); f; frictional coefficient (g/s); g(s*); concentration distribution function (see Fig. 2 legend); η; viscosity (poise); ρ; density (g/mL); n; Fe; number of iron atoms per protein shell as determined by AUC or ferrozine assays; M; molar mass (g/mol); M; r; relative molar mass (unitless); r; Stokes radius (nm); r; m; radius of meniscus (cm); s; Svedberg constant for the protein at stated concentration and temperature in buffer (10; −; 13; s); s; W; weighted average of; s; over the g(s*) curve; s; 20,; w; o; Svedberg constant for infinitely dilute protein in pure water at 20; °C (10; −; 13; s); s; 20,; w; Svedberg constant of protein at stated concentration in pure water at 20; °C (10; −; 13; s); ω; angular velocity (rad/s); σ; linewidth of Gaussian function as defined in the text (svedbergs); ν̅; partial specific volume (mL/g)Ferritin; Analytical ultracentrifugation; Sucrose gradients; Iron mineralization; Nanoparticle preparation
Reactivity of ferritin and the structure of ferritin-derived ferrihydrite by F. Marc Michel; Hazel-Ann Hosein; Douglas B. Hausner; Sudeep Debnath; John B. Parise; Daniel R. Strongin (pp. 871-885).
In nature or in the laboratory, the roughly spherical interior of the ferritin protein is well suited for the formation and storage of a variety of nanosized metal oxy-hydroxide compounds which hold promise for a range of applications. However, the linkages between ferritin reactivity and the structure and physicochemical properties of the nanoparticle core, either native or reconstituted, remain only partly understood.Here we review studies, including those from our laboratory, which have investigated the structure of ferritin-derived ferrihydrite and reactivity of ferritin, both native and reconstituted. Selected proposed structure models for ferrihydrite are discussed along with the structural and genetic relationships that exist among several different forms of ferrihydrite. With regard to reactivity, the review will emphasize studies that have investigated the (photo)reactivity of ferritin and ferritin-derived materials with environmentally relevant gaseous and aqueous species.The inorganic core formed from apoferritin reconstituted with varied amounts of Fe has the same structural topology as the inorganically derived ferrihydrite that is an important component of many environmental and soil systems. Reactivity of ferritin toward aqueous species resulting from the photoexcitation of the inorganic core of the protein shows promise for driving redox reactions relevant to environmental chemistry.Ferritin-derived ferrihydrite is effectively maintained in a relatively unaggregated state, which improves reactivity and opens the possibility of future applications in environmental remediation. Advances in our understanding of the structure, composition, and disorder in synthetic, inorganically derived ferrihydrite are shedding new light on the reactivity and stability of ferrihydrite derived artificially from ferritin.
Keywords: Ferritin; Reconstituted; Ferrihydrite; Atomic arrangements; Structural topology; Ferrihydrite reactivity
The Mössbauer and magnetic properties of ferritin cores by Georgia C. Papaefthymiou (pp. 886-897).
Background: Mössbauer and magnetization measurements, singly or in combination, extract detailed information on the microscopic or internal magnetism of iron-based materials and their macroscopic or bulk magnetization. The combination of the two techniques affords a powerful investigatory probe into spin relaxation processes of nanosize magnetic systems. The ferritin core constitutes a paradigm of such nano-magnetic system where Mössbauer and magnetization studies have been broadly combined in order to elucidate its composition, the initial steps of iron nucleation and biomineralization, particle growth and core-size distribution. In vivo produced and in vitro reconstituted wild-type and variant ferritins have been extensively studied in order to elucidate structure/function correlations and ferritin’s role in iron overloading or neurodegenerative disorders. Scope of Review: Studies on the initial stages of iron biomineralization, biomimetic synthetic analogues and ferrous ion retention within the ferritin core are presented. The dynamical magnetic properties of ferritin by Mössbauer and magnetization measurements are critically reviewed. The focus is on experiments that reveal the internal magnetic structure of the ferritin core. Novel magnetic measurements on individual ferritin molecules via AFM and nanoSQUID investigations are also mentioned. Major Conclusions: A complex two-phase spin system is revealed due to finite-size effects and non-compensated spins at the surface of the anti-ferromagnetic ferritin core. Below the blocking temperature surface spins participate in relaxation processes much faster than those associated with collective magnetic excitations of interior spins. General Significance: The studies reviewed contribute uniquely to the elucidation of the spin-structure and spin-dynamics of anti-ferromagnetic nanolattices and their possible applications to nano/bio-technology.
Keywords: Abbreviations; HoSF; horse spleen ferritin; HuHF; human H-Chain ferritin; δ; isomer shift; Δ; E; Q; quadrupole splitting; AC; alternating current; DC; direct current; ZFC; zero-field-cooled; FC; field-cooled; AFM; atomic force microscopy; SQUID; superconducting quantum interference device; THF; tetrahydrofuran; MRI; magnetic resonance imagingBiomineralization; Superparamagnetism; Finite-size effects; Antiferromagnetic nanoparticles; Core/shell model of ferritin