Understanding the Role of Filamentous Actin in Food Quality: From Structure to Application.

Actin, a multifunctional protein highly expressed in eukaryotes, is widely distributed throughout cells and serves as a crucial component of the cytoskeleton. Its presence is integral to maintaining cell morphology and participating in various biological processes. As an irreplaceable component of myofibrillar proteins, actin, including G-actin and F-actin, is highly related to food quality. Up to now, purification of actin at a moderate level remains to be overcome. In this paper, we have reviewed the structures and functions of actin, the methods to obtain actin, and the relationships between actin and food texture, color, and flavor. Moreover, actin finds applications in diverse fields such as food safety, bioengineering, and nanomaterials. Developing an actin preparation method at the industrial level will help promote its further applications in food science, nutrition, and safety.

A comprehensive review on hemocyanin from marine products: Structure, functions, its implications for the food industry and beyond.

Hemocyanin, an oxygen-transport protein, is widely distributed in the hemolymph of marine arthropods and mollusks, playing an important role in their physiological processes. Recently, hemocyanin has been recognized as a multifunctional glycoprotein involved in the immunological responses of aquatic invertebrates. Consequently, the link between hemocyanin functions and their potential applications has garnered increased attention. This review offers an integrated overview of hemocyanin's structure, physicochemical characteristics, and bioactivities to further promote the utilization of hemocyanin derived from marine products. Specifically, we review its implication in two aspects of food and aquaculture industries: quality and health. Hemocyanin's inducible phenoloxidase activity is thought to be an inducer of melanosis in crustaceans. New anti-melanosis agents targeted to hemocyanin need to be explored. The red-color change observed in shrimp shells is related to hemocyanin, affecting consumer preferences. Hemocyanin's adaptive modification in response to the aquatic environment is available as a biomarker. Additionally, hemocyanin is endowed with bioactivities encompassing anti-microbial, antiviral, and therapeutic activities. Hemocyanin is also a novel allergen and its allergenic features remain incompletely characterized.

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.

Construction of Manganese-Based Oyster (Crassostrea gigas) Ferritin Nanozyme with Catalase-like Enzyme Activity.

MnO2 is a nanozyme that inhibits the decomposition of hydrogen peroxide (H2O2) into a hydroxyl radical (OH•), thus preventing its conversion into reactive oxygen species (ROS). Oyster ferritin (GF1) is a macromolecular protein that provides uniform size and high stability and serves as an excellent template for the biomineralization of nanozyme. This study presents a unique method in which MnO2 is grown in situ in the GF1 cavity, yielding a structurally stable ferritin-based nanozyme (GF1@Mn). GF1@Mn is demonstrated to be stable at 80 °C and pH 4-8, exhibiting a higher affinity with H2O2 than many other catalases (CAT) with a Michaelis constant (Km) of 25.45 mmol/L. In vitro experiments have demonstrated the potential of GF1@Mn to enhance cell survival by reducing nitric oxide (NO) production while mitigating macrophage damage from ROS. The findings are essential to developing ferritin-based nanozymes and hold great potential for applications in functional food development.

Preparation and Unique Three-Dimensional Self-Assembly Property of Starfish Ferritin.

The structure and assembly properties of ferritin derived from aquatic products remain to be explored. Constructing diverse three-dimensional (3D) protein architectures with the same building blocks has important implications for nutrient delivery, medicine and materials science. Herein, ferritin from Asterias forbesii (AfFer) was prepared, and its crystal structure was resolved at 1.91 Å for the first time. Notably, different from the crystal structure of other reported ferritin, AfFer exhibited a BCT lattice arrangement in its crystals. Bioinspired by the crystal structure of AfFer, we described an effective approach for manufacturing 3D porous, crystalline nanoarchitectures by redesigning the shared protein interface involved in different 3D protein arrays. Based on this strategy, two 3D superlattices of body-centered tetragonal and simple cubicwere constructed with ferritin molecules as the building blocks. This study provided a potentially generalizable strategy for constructing different 3D protein-based crystalline biomaterials with the same building blocks.

Characterization and Structural Analyses of Enolase from Shrimp (Litopenaeus vannamei).

Transcriptome analysis had recognized enolase from shrimp Litopenaeus vannamei (L. vannamei), which is termed LvEnolase, as one of the allergens, but its amino acid sequence and protein structure have been lacking. In this study, natural LvEnolase was isolated from L. vannamei and characterized for the first time. The full-length cDNA sequence of LvEnolase was effectively cloned, which encoded 434 amino acid residues. The crystal structure of LvEnolase was successfully determined at a resolution of 2.5 Å by X-ray crystallography (PDB: 8UEL). Notably, it was observed that near the active center, a loop exists in either an open or closed state, and the open loop was associated with the product release phase. Furthermore, enzyme activity assays were conducted to validate the catalytic capabilities of purified LvEnolase. These findings significantly enhance our comprehension of the enolase family and provide valuable support for delving into the functions and characteristics of LvEnolase.

Shape-Anisotropic Assembly of Protein Nanocages with Identical Building Blocks by Designed Intermolecular π-π Interactions.

Protein lattices that shift the structure and shape anisotropy in response to environmental cues are closely coupled to potential functionality. However, to design and construct shape-anisotropic protein arrays from the same building blocks in response to different external stimuli remains challenging. Here, by a combination of the multiple, symmetric interaction sites on the outer surface of protein nanocages and the tunable features of phenylalanine-phenylalanine interactions, a protein engineering approach is reported to construct a variety of superstructures with shape anisotropy, including 3D cubic, 2D hexagonal layered, and 1D rod-like crystalline protein nanocage arrays by using one single protein building block. Notably, the assembly of these crystalline protein arrays is reversible, which can be tuned by external stimuli (pH and ionic strength). The anisotropic morphologies of the fabricated macroscopic crystals can be correlated with the Å-to-nm scale protein arrangement details by crystallographic elucidation. These results enhance the understanding of the freedom offered by an object's symmetry and inter-object π-π stacking interactions for protein building blocks to assemble into direction- and shape-anisotropic biomaterials.

Advanced Insights into Walnut Protein: Structure, Physiochemical Properties and Applications.

Facing extreme pressure from an increasing population and climate degeneration, it is important to explore a green, safe and environmentally sustainable food source, especially for protein-enriched diets. Plant proteins have gained much attention in recent years, ascribing to their high nutritional value and environmental friendliness. In this review, we summarized recent advances in walnut protein with respect to its geographical distribution, structural and physiochemical properties and functional attributes. As a worldwide cultivated and largely consumptive crop, allergies and some physicochemical limitations have also led to a few concerns about walnut protein. Through comprehensive analysis and discussion, some strategies may be useful for future research, extraction and processing of walnut protein.

Oyster (Crassostrea gigas) ferritin relieves lead-induced liver oxidative damage via regulating the mitophagy.

Lead can induce oxidative stress and increase lipid peroxidation in biofilms, leading to liver damage and physiological dysfunction. This study aimed to investigate how oyster ferritin (GF1) attenuates lead-induced oxidative damage to the liver in vitro and in vivo. Animal experiments have confirmed that lead exposure can lead to oxidative damage and lipid peroxidation of the liver, and ferritin can regulate the activity of antioxidant enzymes and alleviate pathological changes in the liver. At the same time, oyster ferritin can regulate the expression of oxidative stress-related genes and reduce the expression of inflammasome-related genes. In addition, lead can induce apoptosis and mitophagy, leading to overproduction of reactive oxygen species and cell death, which can be effectively alleviated by oyster ferritin. Overall, this study provides a theoretical foundation for the use of oyster ferritin as a means of mitigating and preventing lead-induced damage.

Highly Stretchable, Transparent, and Adhesive Double-Network Hydrogel Dressings Tailored with Fish Gelatin and Glycyrrhizic Acid for Wound Healing.

It remains challenging to fabricate highly stretchable and adhesive hydrogel dressings for wound healing using simple, safe, and green methods. Herein, inspired by the main components of snail mucus, a fully physical double-network (DN) hydrogel dressing composed of fish gelatin (FGel) and glycyrrhizic acid (GL) was fabricated, in which FGel provided a protein scaffold to mimic snail mucus proteins, while GL mimicked the adhesion and bioactivity of snail mucus because of its abundant carboxyl and hydroxyl groups and intrinsic immunomodulatory activity. As expected, the obtained FGel/GL hydrogel dressings exhibited outstanding mechanical and adhesive performances (flexibility, stretchability, adhesive ability, and removability), high transparency, and good antifreezing properties. More importantly, they also possessed excellent biocompatibility, cell migration, and angiogenesis ability in vitro experiments. Finally, animal experiments in vivo indicated that the FGel/GL hydrogel dressings significantly promoted full-thickness wound healing, including promoting granulation tissue formation, collagen deposition, and skin angiogenesis and inhibiting the inflammatory response. All these findings indicated that the FGel/GL hydrogel dressings have great potential for applications in the clinical treatment of wound healing.

Oyster ferritin can efficiently alleviate ROS-mediated inflammation attributed to its unique micro-environment around three-fold channels.

The conversion of toxic Fe2+ into non-toxic Fe3+ stored in the inner cavity of ferritin nanocage could effectively reduce the occurrence of the Fenton reaction and inhibit the formation of harmful reactive oxygen species (ROS). In this study, we reveal that oyster ferritin (GF1) can rely on its high catalytic activity (7.7 times that of rHuHF) and high binding ability of Fe2+ (9.1 times that of rHuHF) to reduce the precursors of Fenton reaction, thus inhibiting the occurrence of Fenton reaction and slowing down reactive oxygen species-mediated inflammation. The above significant advantage of GF1 can be attributed to the Asp at the position 120th, which could increase the negatively charged area of three-fold channels from 37.8% (rHuHF) to 67.8% and then enhance its oxidation rate and ability of GF1. The findings are of great value in advancing novel nanoparticle drug design based on crystalline structure.

Zinc nutrition and dietary zinc supplements.

As the second most abundant trace element in the human body, zinc nutrition is constantly a hot topic. More than one-third population is suffering zinc deficiency, which results in various types of diseases or nutritional deficiencies. Traditional ways of zinc supplementation seem with low absorption rates and significant side effects. Zinc supplements with dietary components are easily accessible and improve zinc utilization rate significantly. Also, mechanisms of maintaining zinc homeostasis are of broad interest. The present review focuses on zinc nutrition in human health in inductive methods. Mainly elaborate on different diseases relating to zinc disorder, highlighting the impact on the immune system and the recent COVID-19. Then raise food-derived zinc-binding compounds, including protein, peptide, polysaccharide, and polyphenol, and also analyze their possibilities to serve as zinc complementary. Finally, illustrate the way to maintain zinc homeostasis and the corresponding mechanisms. The review provides data information for maintaining zinc homeostasis with the food-derived matrix.

Oyster (Crassostrea gigas) ferritin should be a promising Fe2+ nanocarrier.

Ferritin, one of the storage forms of iron, which widely exists in all living organisms and shows its potential as functional nanomaterial. In this study, Fe2+ were added to oyster ferritin (GF1) in vitro until reached experimental saturation state. The structure characterization and monodisperse morphology of ferritin were showed that the protein structure of ferritin did not change significantly after adding Fe2+ and GF1 with 1000 Fe2+ (GF1-1000 Fe2+) was selected for subsequent experiments. The storage stability results showed that 11.27 % of the protein remained cage-like structure when GF1-1000 Fe2+ was stored at 4 °C for 12 days. The thermal treatment results showed that GF1-1000 Fe2+ still maintained certain structure and activity at 80 °C, and 82.8 % of Fe2+ was still retained at 80 °C. These experimental results may provide a theoretical basis for the development of novel iron supplement that are non-toxic and highly stable.

A natural strategy for astaxanthin stabilization and color regulation: Interaction with proteins.

The pigment astaxanthin, one of the carotenoids, is regarded as a functional factor with various biological activities, widely applied in feed, nutraceutical, and cosmetic industries. However, its low stability and poor water solubility limit its application. Examples in nature suggest that binding to proteins is a simple and effective method to improve the stability and bioavailability of astaxanthin. Proteins from algae, fish, and crustaceans have all been demonstrated to have astaxanthin-binding capacity. Inspired by nature, artificial astaxanthin-protein systems have been established in foods. Binding to proteins could bring aquatic species various colors, and changes in the conformation of astaxanthin after binding to proteins leads to color changes. The review innovatively summarizes multiple examples of proteins as means of protecting astaxanthin, giving a reference for exploring and analyzing pigment-protein interactions and providing a strategy for carotenoids stabilization and color regulation, which is beneficial to the broader and deeper applications of carotenoids.

Spatiotemporal control over 3D protein nanocage superlattices for the hierarchical encapsulation and release of different cargo molecules.

Taking inspiration from Nature, we have constructed a two-compartment system based on 3D ferritin nanocage superlattices, the self-assembly behavior of which can be spatiotemporally controlled using two designed switches. One pH switch regulates the assembly of the ferritin subunit into its shell-like structure, whereas the other metal switch is responsible for assembly of the 3D superlattices from ferritin nanocages as building blocks. Consequently, this system holds great promise for the hierarchical encapsulation and release of two different cargo molecules.

Dietary Heme-Containing Proteins: Structures, Applications, and Challenges.

Heme-containing proteins, commonly abundant in red meat and blood, are considered promising dietary sources for iron supplementation and fortification with higher bioavailability and less side effects. As the precise structures and accurate bioactivity mechanism of various heme-containing proteins (hemoglobin, myoglobin, cytochrome, etc.) are determined, many methods have been explored for iron fortification. Based on their physicochemical and biological functions, heme-containing proteins and the hydrolyzed peptides have been also widely utilized as food ingredients and antibacterial agents in recent years. In this review, we summarized the structural characterization of hemoglobin, myoglobin, and other heme proteins in detail, and highlighted recent advances in applications of naturally occurring heme-containing proteins as dietary iron sources in the field of food science and nutrition. The regulation of absorption rate, auto-oxidation process, and dietary consumption of heme-containing proteins are then discussed. Future outlooks are also highlighted with the aim to suggest a research line to follow for further studies.

Microencapsulation of Carvacrol by Complex Coacervation of Walnut Meal Protein Isolate and Gum Arabic: Preparation, Characterization and Bio-Functional Activity.

As a natural phenolic compound, carvacrol has attracted much attention due to its excellent antibacterial and antioxidant activities. However, its application is limited due to its instability, such as easy volatilization, easy oxidation, etc. Protein-polysaccharide interactions provide strategies for improving their stability issues. In this study, the plant-based carvacrol microcapsules via complex coacervation between walnut meal protein isolate (WMPI) and gum Arabic (GA) has been fabricated and characterized. The formation conditions of WMPI-GA coacervates were determined by some parameters, such as pH, zeta-potential, and turbidity. The optimum preparation conditions were achieved at pH 4.0 with a WMPI-to-GA ratio of 6:1 (w/w). The mean particle size, loading capacity (LC), and encapsulation efficiency (EE) of the microcapsules were 43.21 µm, 26.37%, and 89.87%, respectively. Fourier transform infrared spectroscopy (FT-IR) and fluorescence microscopy further confirmed the successful microencapsulation of carvacrol. The microencapsulation of carvacrol improved the thermal stability of the free carvacrol. The swelling capacity results indicated that it could resist gastric acid, and facilitate its intestinal absorption. Meanwhile, the carvacrol molecules trapped within the microcapsules could be continuously released in a concentration-dependent manner. Furthermore, the microcapsules presented good antioxidant activity and antibacterial activity against the Gram-negative (E. coli) and the Gram-positive (S. aureus) bacteria. These results indicated that the obtained carvacrol microcapsules have a potential application value as a food preservative in the food industry.

Directed Self-Assembly of Dimeric Building Blocks into Networklike Protein Origami to Construct Hydrogels.

Engineering proteins to construct self-assemblies is of crucial significance not only for understanding the sophisticated living systems but also for fabricating advanced materials with unexplored functions. However, due to the inherent chemical heterogeneity and structural complexity of the protein surface, designing complex protein assemblies in an anisotropic fashion remains challenging. Here, we describe a self-assembly approach to fabricating protein origami with a networklike structure by designing dual noncovalent interactions on the different positions of a single protein building block. With dimeric proteins as building blocks, 1D protein filaments were constructed by the designed metal coordination at key protein interfaces. Subsequently, the network superstructures were created by the cross-linking of the 1D protein filaments at branch point linkages through the second designed π-π stacking interactions. Notably, upon increasing the protein concentration, the formed protein networks convert into hydrogels with reversible, injectable, and self-healing properties, which have the ability to promote bone regeneration. This strategy could be used to fabricate other protein-based materials with unexplored functions.

Construction of Sol-Gel Phase-Reversible Hydrogels with Tunable Properties with Native Nanofibrous Protein as Building Blocks.

Reversible sol-gel transforming behaviors combined with tunable mechanical properties are vital demands for developing biomaterials. However, it remains challenging to correlate these properties with the hydrogels constructed by denatured protein as building blocks. Herein, taking advantage of naturally high-affinity coordination environments consisting of i, i + 4 His-Glu motifs offered by paramyosin, a ubiquitous nanofibrous protein, we found that Zn2+ rather than Ca2+ or Mg2+ has the ability to trigger the self-assembly of native abalone paramyosin (AbPM) into protein hydrogels under benign conditions, while the addition of EDTA induces the hydrogels back into protein monomers, indicative of a reversible process. By using such sol-gel reversible property, the AbPM gels can serve as a vehicle to encapsulate bioactive molecules such as curcumin, thereby protecting it from degradation from thermal and photo treatment. Notably, based on the high conserved structure of native AbPM, the mechanical property and biological activity of the fabricated AbPM hydrogels can be fined-tuned by its noncovalent interaction with small molecules. All these findings raise the possibility that native paramyosin can be explored as a new class of protein hydrogels which exhibit favorable properties that the traditional hydrogels constructed by denatured protein building blocks do not have.

Zinc binding strength of proteins dominants zinc uptake in Caco-2 cells.

Zinc plays a vital role in structural, catalysis, and signal regulation in the human body. Zinc deficiency leads to the dysfunction of many organs and immunity systems. Diet proteins have distinct effects on zinc uptake. However, the mechanisms are uncovered. Here we select three principal components from whey protein: alpha-lactalbumin, beta-lactoglobulin, and bovine serum albumin, which bind with zinc at different affinities, to evaluate the relationship between their potential zinc uptake and protein binding. The experimental data shows that beta-lactoglobulin could promote zinc uptake, alpha-lactalbumin has minor effects, whereas bovine serum albumin reduced zinc uptake in Caco-2 cell lines. Zinc binding effects on protein structure were thoroughly inspected through fluorescent spectroscopy and X-ray crystallography. Isothermal titration calorimetry revealed that three proteins have different binding affinities toward zinc ions. We speculate that protein binding eliminates toxic effects from free zinc, and the binding strength dominates zinc uptake.