Combinatorial accumulation, stress response, detoxification and synaptic transmission effects of cadmium and selenium in clams Ruditapes philippinarum

This study investigated the toxicological effects and mechanisms of cadmium (Cd) (5 and 50 μg/L) and selenium (Se) (3 and 30 μg/L) at environmentally relevant concentrations on the gills and digestive glands of clams Ruditapes philippinarum. Results indicated that Cd and Se could tissue-specifically impact osmoregulation, energy metabolism, and synaptic transmission in the gills and digestive glands of clams. After exposure to 50 μg/L Cd, the digestive glands of clams up-regulated the expression of methionine-gamma-lyase and metallothionein for detoxification. Clam digestive glands exposed to 3 μg/L Se up-regulated the expression of catalase and glutathione peroxidase to alleviate oxidative stress, and down-regulated the expression of selenide-water dikinase to reduce the conversion of inorganic Se. Additionally, the interaction mode between Cd and Se largely depended on their molar ratio, with a ratio of 11.71 (50 μg/L Cd + 3 μg/L Se) demonstrated to be particularly harmful, as manifested by significantly more lesions, oxidative stress, and detoxification demand in clams than those exposed to Cd or Se alone. Collectively, this study revealed the complex interaction patterns and mechanisms of Cd and Se on clams, providing a reference for exploring their single and combined toxicity.

Advancements of the Molecular Directed Design and Structure-Activity Relationship of Ferritin Nanocage

Ferritin nanocages possess remarkable structural properties and biological functions, making them highly attractive for applications in functional materials and biomedicine. This comprehensive review presents an overview of the molecular characteristics, extraction and identification of ferritin, ferritin receptors, as well as the advancements in the directional design of high-order assemblies of ferritin and the applications based on its unique structural properties. Specifically, this Review focuses on the regulation of ferritin assembly from one to three dimensions, leveraging the symmetry of ferritin and modifications on key interfaces. Furthermore, it discusses targeted delivery of nutrition and drugs through facile loading and functional modification of ferritin. The aim of this Review is to inspire the design of micro/nano functional materials using ferritin and the development of nanodelivery vehicles for nutritional fortification and disease treatment.

Structural and Biochemical Characterization of Silver/Copper Binding by Dendrorhynchus zhejiangensis Ferritin

Ferritin with a highly symmetrical cage-like structure is not only key in the reversible storage of iron in efficient ferroxidase activity; it also provides unique coordination environments for the conjugation of heavy metal ions other than those associated with iron. However, research regarding the effect of these bound heavy metal ions on ferritin is scarce. In the present study, we prepared a marine invertebrate ferritin from Dendrorhynchus zhejiangensis (DzFer) and found that it could withstand extreme pH fluctuation. We then demonstrated its capacity to interact with Ag⁺ or Cu²⁺ ions using various biochemical and spectroscopic methods and X-ray crystallography. Structural and biochemical analyses revealed that both Ag⁺ and Cu²⁺ were able to bind to the DzFer cage via metal-coordination bonds and that their binding sites were mainly located inside the three-fold channel of DzFer. Furthermore, Ag⁺ was shown to have a higher selectivity for sulfur-containing amino acid residues and appeared to bind preferentially at the ferroxidase site of DzFer as compared with Cu²⁺. Thus, it is far more likely to inhibit the ferroxidase activity of DzFer. The results provide new insights into the effect of heavy metal ions on the iron-binding capacity of a marine invertebrate ferritin.

Structural and Functional Insights into the Roles of Potential Metal-Binding Sites in Apostichopus japonicus Ferritin

Ferritin is widely acknowledged as a conservative iron storage protein found in almost all living kingdoms. Apostichopus japonicus (Selenka) is among the oldest echinoderm fauna and has unique regenerative potential, but the catalytic mechanism of iron oxidation in A. japonicus ferritin (AjFER) remains elusive. We previously identified several potential metal-binding sites at the ferroxidase center, the three- and four-fold channels in AjFER. Herein, we prepared AjFER, AjFER-E25A/E60A/E105A, AjFER-D129A/E132A, and AjFER-E168A mutants, investigated their structures, and functionally characterized these ferritins with respect to Fe2+ uptake using X-ray techniques together with biochemical analytical methods. A crystallographic model of the AjFER-D129A/E132A mutant, which was solved to a resolution of 1.98 Å, suggested that the substitutions had a significant influence on the quaternary structure of the three-fold channel compared to that of AjFER. The structures of these ferritins in solution were determined based on the molecular envelopes of AjFER and its variants by small-angle X-ray scattering, and the structures were almost consistent with the characteristics of well-folded and globular-shaped proteins. Comparative biochemical analyses indicated that site-directed mutagenesis of metal-binding sites in AjFER presented relatively low rates of iron oxidation and thermostability, as well as weak iron-binding affinity, suggesting that these potential metal-binding sites play critical roles in the catalytic activity of ferritin. These findings provide profound insight into the structure-function relationships related to marine invertebrate ferritins.

Influence of magnetized water irrigation on characteristics of antioxidant enzyme, ferritin, and Cd excretion in Festuca arundinacea during phytoextraction

The magnetic field can alter the hydrogen-bond structure and polarity characteristics of water; therefore, we hypothesize that magnetized water can affect plant physiological functions, including metal detoxification and excretion. In this study, the amount of Cd excreted on the leaves of Festuca arundinacea was estimated using magnetized water and normal water irrigation patterns. Irrigation with magnetized water improved the shoot dry weight and Cd content in F. arundinacea by 13.6% and 52.8%, respectively, compared to the control. Magnetized water irrigation also increased antioxidant enzyme activities in plant leaves, thereby alleviating the oxidative damage. The concentration of ferritin was 0.91 folds higher than that of the control, increasing the Fe sequestration and detoxification capacity of F. arundinacea. The amount of Cd excreted was significantly higher under magnetized water irrigation, thereby increasing the annual Cd removal by 109.7% from soil by leaf washing compared with that of the control. In contrast, F. arundinacea irrigated with magnetized water excreted 38.1% less Fe owing to the increase in ferritin levels, compared with that of the control. This study suggests a novel pathway of Cd phytoremediation by rinsing excreted Cd from the leaf surface without harvesting and replanting F. arundinacea.

Ferritin: A Promising Nanoreactor and Nanocarrier for Bionanotechnology

The essence of bionanotechnology lies in the application of nanotechnology/nanomaterials to solve the biological problems. Quantum dots and nanoparticles hold potential biomedical applications, but their inherent problems such as low solubility and associated toxicity due to their interactions at nonspecific target sites is a major concern. The self-assembled, thermostable, ferritin protein nanocages possessing natural iron scavenging ability have emerged as a potential solution to all the above-mentioned problems by acting as nanoreactor and nanocarrier. Ferritins, the cellular iron repositories, are hollow, spherical, symmetric multimeric protein nanocages, which sequester the excess of free Fe(II) and synthesize iron biominerals (Fe₂O₃·H₂O) inside their ∼5-8 nm central cavity. The electrostatics and dynamics of the pore residues not only drives the natural substrate Fe²⁺ inside ferritin nanocages but also uptakes a set of other metals ions/counterions during in vitro synthesis of nanomaterial. The current review aims to report the recent developments/understanding on ferritin structure (self-assembly, surface/pores electrostatics, metal ion binding sites) and chemistry occurring inside these supramolecular protein cages (protein mediated metal ion uptake and mineralization/nanoparticle formation) along with its surface modification to exploit them for various nanobiotechnological applications. Furthermore, a better understanding of ferritin self-assembly would be highly useful for optimizing the incorporation of nanomaterials via the disassembly/reassembly approach. Several studies have reported the successful engineering of these ferritin protein nanocages in order to utilize them as potential nanoreactor for synthesizing/incorporating nanoparticles and as nanocarrier for delivering imaging agents/drugs at cell specific target sites. Therefore, the combination of nanoscience (nanomaterials) and bioscience (ferritin protein) projects several benefits for various applications ranging from electronics to medicine.

Oyster (Crassostrea gigas) ferritin can efficiently reduce the damage of Pb2+in vivo by electrostatic attraction

Heavy metal ions pollution can cause damage to human body through food, so the development of a new kind of macromolecular that can remove heavy metal ions damage has a good application prospect. The possibilities of removing heavy metal ions from food system with ferritin were studied in this paper. In this study, oyster ferritin (GF1) can resistant to denaturation induced by Pb²⁺, Cd²⁺, Cr³⁺ and still maintains its basic structure. GF1 can bind more Pb²⁺, Cd²⁺, Cr³⁺ than recombinant human H-chain ferritin (rHuHF), especially Pb²⁺, and the findings suggest that each GF1 can capture about 51.42 Pb²⁺ in solution. The hard and soft acids and base also verifies that Pb²⁺ have stronger binding ability to the key amino acids at the outer end of the three-fold symmetry channel. Cells preprotected by ferritin could resistant to heavy metal ions. And GF1 can reduce the high blood lead in mice and may play a role in alleviating lead poisoning in vivo. All findings demonstrated that GF1 can be used as a novel macromolecule to bind heavy metal ions, and the study can broaden the research scope of ferritin in contaminated food systems.

Structural Insights Into the Effects of Interactions With Iron and Copper Ions on Ferritin From the Blood Clam Tegillarca granosa

In addition to its role as an iron storage protein, ferritin can function as a major detoxification component in the innate immune defense, and Cu²⁺ ions can also play crucial antibacterial roles in the blood clam, Tegillarca granosa. However, the mechanism of interaction between iron and copper in recombinant Tegillarca granosa ferritin (TgFer) remains to be investigated. In this study, we investigated the crystal structure of TgFer and examined the effects of Fe²⁺ and Cu²⁺ ions on the TgFer structure and catalytic activity. The crystal structure revealed that TgFer presented a typically 4–3–2 symmetry in a cage-like, spherical shell composed of 24 identical subunits, featuring highly conserved organization in both the ferroxidase center and the 3-fold channel. Structural and biochemical analyses indicated that the 4-fold channel of TgFer could be serviced as potential binding sites of metal ions. Cu²⁺ ions appear to bind preferentially with the 3-fold channel as well as ferroxidase site over Fe²⁺ ions, possibly inhibiting the ferroxidase activity of TgFer. Our results present a structural and functional characterization of TgFer, providing mechanistic insight into the interactions between TgFer and both Fe²⁺ and Cu²⁺ ions.

Crystallographic characterization of a marine invertebrate ferritin from the sea cucumber Apostichopus japonicus

Ferritin is considered to be an ubiquitous and conserved iron-binding protein that plays a crucial role in iron storage, detoxification and immune response. Although ferritin is of critical importance for almost all kingdoms of life, there is a lack of knowledge about its role in the marine invertebrate sea cucumber (Apostichopus japonicus). In this study, we characterized the first crystal structure of Apostichopus japonicas ferritin (AjFER) at 2.75 Å resolution. The structure of AjFER shows a 4-3-2 symmetry cage-like hollow shell composed of 24 subunits, mostly similar to the structural characteristics of other known ferritin species, including the conserved ferroxidase center and 3-fold channel. The 3-fold channel consisting of three 3-fold negative amino acid rings suggests a potential pathway in which metal ions can be first captured by Asp120 from the outside environment, attracted by His116 and Cys128 when entering the channel, and then transferred by Glu138 from the 3-fold channel to the ferroxidase site. Overall, the presented crystal structure of AjFER may provide insights into the potential mechanism of the metal transport pathway for related marine invertebrate ferritins.

Bioengineered Microbes for Soil Health Restoration - Present Status and Future

According to the United Nations Environment Programme (UNEP), soil health is declining over the decades and it has an adverse impact on human health and food security. Hence, soil health restoration is a need of the hour. It is known that microorganisms play a vital role in remediation of soil pollutants like heavy metals, pesticides, hydrocarbons, etc. However, the indigenous microbes have a limited capacity to degrade these pollutants and it will be a slow process. Genetically modified organisms (GMOs) can catalyze the degradation process as their altered metabolic pathways lead to hypersecretions of various biomolecules that favor the bioremediation process. This review provides an overview on the application of bioengineered microorganisms for the restoration of soil health by degradation of various pollutants. It also sheds light on the challenges of using GMOs in environmental application as their introduction may affect the normal microbial community in soil. Since soil health also refers to the potential of native organisms to survive, the possible changes in the native microbial community with the introduction of GMOs are also discussed. Finally, the future prospects of using bioengineered microorganisms in environmental engineering applications to make the soil fertile and healthy have been deciphered. With the alarming rates of soil health loss, the treatment of soil and soil health restoration need to be fastened to a greater pace and the combinatorial efforts unifying GMOs, plant growth-promoting rhizobacteria, and other soil amendments will provide an effective solution to soil heath restoration ten years ahead.

Integrative proteomics and metabolomics profiling of the protective effects of Phascolosoma esculent ferritin on BMSCs in Cd(II) injury

Ferritin is the major intracellular iron storage protein and is essential for iron homeostasis and detoxification. Cadmium affects cellular homeostasis and induces cell toxicity via sophisticated mechanisms. Here, we aimed to explore the mechanisms of cytoprotective effect of Phascolosoma esculenta ferritin (PeFer) on Cd(II)-induced bone marrow mesenchymal stem cell (BMSC) injury. Herein, the effects of different treated groups on apoptosis and cell cycle were assessed using flow cytometric analysis. We further investigated the alterations of the three groups using integrative 2-DE-based proteomics and 1H NMR-based metabolomics profiles. The results indicate that PeFer reduces BMSC apoptosis induced by Cd(II) and delays G0/G1 cell cycle progression. A total of 19 proteins and 70 metabolites were significantly different among BMSC samples of the three groups. Notably, multiomics analysis revealed that Cd(II) might perturb the ER stress-mediated apoptosis pathway and disrupt biological processes related to the TCA cycle, amino acid metabolism, purine and pyrimidine metabolism, thereby suppressing the cell growth rate and initiating apoptosis; however, the addition of PeFer might protect BMSCs against cell apoptosis to improve cell survival by enhancing energy metabolism. This study provides a better understanding of the underlying molecular mechanisms of the protective effect of PeFer in BMSCs against Cd(II) injury.

Structure determination of ferritin from Dendrorhynchus zhejiangensis

Ferritin is an important hub of iron metabolism because it stores iron during times of iron overload and releases iron during iron deficiency. Here, we present the first crystal structure of ferritin from the marine invertebrate Dendrorhynchus zhejiangensis with a 2.3 Å resolution. D. zhejiangensis ferritin (DzFer) exhibits a common cage-shaped hollow sphere with 24 subunits containing the ferroxidase centers and 3-fold and 4-fold channels. The structure of DzFer shows highly conserved catalytic residues in the ferroxidase center. The metal wire formed by ferrous ions in the 3-fold channel reveals the path that iron ions use to enter and translocate into the ferroxidase site to be oxidized and finally arrive at the nucleation site. However, the electrostatic environment of the channels and pores exhibits significant and extensive variability, suggesting that ferritins execute diverse functions in different environments.

Crystallographic characterization of ferritin from Sinonovacula constricta

Ferritins are ubiquitous iron-binding proteins that are mainly related to iron storage, detoxification and innate immunity. Here, we present the crystal structure of a marine invertebrate ferritin from Sinonovacula constricta at a resolution of 1.98 Å. The S. constricta ferritin (ScFer) possessed some structural similarities with vertebrate ferritins, and they shared a well-conserved architecture composed of five α-helical bundles that assembled into a cage-like structure with 24-subunits. The structure of ScFer also showed iron binding sites in the 3-fold channel, ferroxidase center, and putative nucleation sites. Further, electrostatic potential calculations suggested that the electrostatic gradient of the 3-fold channel could provide a guidance mechanism for iron entering the ferritin cavity.