The chicken egg white proteome

The anti-bacterial iron-restriction defence mechanisms of egg white; the potential role of three lipocalin-like proteins in resistance against Salmonella

Salmonella enterica serovar Enteritidis (SE) is the most frequently-detected Salmonella in foodborne outbreaks in the European Union. Among such outbreaks, egg and egg products were identified as the most common vehicles of infection. Possibly, the major antibacterial property of egg white is iron restriction, which results from the presence of the iron-binding protein, ovotransferrin. To circumvent iron restriction, SE synthesise catecholate siderophores (i.e. enterobactin and salmochelin) that can chelate iron from host iron-binding proteins. Here, we highlight the role of lipocalin-like proteins found in egg white that could enhance egg-white iron restriction through sequestration of certain siderophores, including enterobactin. Indeed, it is now apparent that the egg-white lipocalin, Ex-FABP, can inhibit bacterial growth via its siderophore-binding capacity in vitro. However, it remains unclear whether Ex-FABP performs such a function in egg white or during bird infection. Regarding the two other lipocalins of egg white (Cal-γ and α-1-glycoprotein), there is currently no evidence to indicate that they sequester siderophores.

Life history shapes variation in egg composition in the blue tit Cyanistes caeruleus

Maternal investment directly shapes early developmental conditions and therefore has long-term fitness consequences for the offspring. In oviparous species prenatal maternal investment is fixed at the time of laying. To ensure the best survival chances for most of their offspring, females must equip their eggs with the resources required to perform well under various circumstances, yet the actual mechanisms remain unknown. Here we describe the blue tit egg albumen and yolk proteomes and evaluate their potential to mediate maternal effects. We show that variation in egg composition (proteins, lipids, carotenoids) primarily depends on laying order and female age. Egg proteomic profiles are mainly driven by laying order, and investment in the egg proteome is functionally biased among eggs. Our results suggest that maternal effects on egg composition result from both passive and active (partly compensatory) mechanisms, and that variation in egg composition creates diverse biochemical environments for embryonic development.

Domestic Fowl Breed Variation in Egg White Protein Expression: Application of Proteomics and Transcriptomics

Avian egg white is essential for protecting and nourishing bird embryos during their development. Being produced in the female magnum, variability in hen oviduct gene expression may affect egg white composition in domestic chickens. Since traditional poultry breeds may represent a source of variation, in the present study we describe the egg white proteome (mass spectrometry) and corresponding magnum transcriptome (high-throughput sequencing) for 20 hens from five domestic fowl breeds (large breeds: Araucana, Czech golden pencilled, Minorca; and small breeds: Booted bantam, Rosecomb bantam). In total, we identified 189 egg white proteins and 16391 magnum-expressed genes. The majority of egg white protein content comprised proteins with an antimicrobial function. Despite general similarity, Between-class Principal Component Analysis revealed significant breed-specific variability in protein abundances, differentiating especially small and large breeds. Though we found strong association between magnum mRNA expression and egg white protein abundance across genes, coinertia analysis revealed no transcriptome/proteome costructure at the individual level. Our study is the first to show variation in protein abundances in egg white across chicken breeds with potential effects on egg quality, biosafety, and chick development. The observed interindividual variation probably results from post-transcriptional regulation creating a discrepancy between proteomic and transcriptomic data.

Dynamics of Structural Barriers and Innate Immune Components during Incubation of the Avian Egg: Critical Interplay between Autonomous Embryonic Development and Maternal Anticipation

The integrated innate immune features of the calcareous egg and its contents are a critical underpinning of the remarkable evolutionary success of the Aves clade. Beginning at the time of laying, the initial protective structures of the egg, i.e., the biomineralized eggshell, egg-white antimicrobial peptides, and vitelline membrane, are rapidly and dramatically altered during embryonic development. The embryo-generated extra-embryonic tissues (chorioallantoic/amniotic membranes, yolk sac, and associated chambers) are all critical to counteract degradation of primary egg defenses during development. With a focus on the chick embryo (Gallus gallus domesticus), this review describes the progressive transformation of egg innate immunity by embryo-generated structures and mechanisms over the 21-day course of egg incubation, and also discusses the critical interplay between autonomous development and maternal anticipation.

Comparative analysis of structure and strength of vitelline membrane and physical parameters of yolk of ostrich, emu, and greater rhea eggs

In this study, we analyzed selected morphological traits of eggs, as well as structure, strength, and protein composition of the vitelline membrane (VM) of ostrich, emu, and greater rhea eggs. Ninety eggs (30 for species) were analyzed for the following parameters: egg weight, yolk weight, yolk ratio, and yolk index. In addition, pH value, water activity, consistency index, and flow behavior index were determined. The strength of VM was measured using the TA.HDPlus Texture Analyzer. Micrograph images were taken via a scanning electron microscope. Polyacrylamide gel electrophoresis was conducted under denaturing conditions. Ostrich eggs were characterized by the highest egg and yolk weight compared with those of emu and greater rhea eggs, whereas emu eggs had the highest yolk ratio compared with those of ostrich and greater rhea eggs (P > 0.05). Yolk content differed among the species in terms of water activity; it was found to be higher in emu eggs than in ostrich and greater rhea eggs (P > 0.05). Based on flow curves, yolks of the ratites were classified as pseudoplastic non-Newtonian fluids. The consistency index was significantly higher in yolks of ostrich and emu than that of greater rhea eggs, whereas the VM of yolks of greater rhea eggs was the most resistant (had the highest breaking force = 26.4 g). All species differed significantly regarding the structure of VM, the outer layer (OL) in particular, which was found to constitute fibers of various thicknesses that were differently arranged. Fibers of the OL of the VM of emu, whose fibers were the least differentiated but formed the most compact network, were the most diverse in characterization. An electropherogram of the VM of ostrich revealed 11 primary protein bands: 6 for the OL and 5 for the inner layer (IL), that of emu revealed 9 bands: 5 for the OL and 4 for the IL, and that of greater rhea revealed 10 bands: 6 for the OL and 4 for the IL.

Molecular characterization of a novel ovodefensin gene in chickens

Host defense peptides (HDPs) represent a large group of diverse small peptides that play important roles in host defense and disease resistance. In vertebrates, one of the main types of HDPs belong to defensins, which are less than 100 amino acid residues and characterized by a highly conserved motif of cysteine residues. Recently, a subfamily of defensins, namely ovodefensins (OvoDs), has been identified in birds and reptiles. However, both their family members and evolutionary relationships remain unclear. In the present study, we cloned and characterized a novel gene namely OvoDBβ in chickens. Our results showed that the full length of chicken OvoDBβ mRNA contains 344 bp nucleotides and encodes a 61-amino acid protein. We further revealed that the mRNA of OvoDBβ is abundant in the oviduct of laying hens but absent in many other tissues. Additionally, sequences comparison and analyses suggested that OvoDBβ is orthologous to the gene previously known as zebra finch OvoDB1, albeit it might exhibit specific structures. Furthermore, both OvoDBα and OvoDBβ were existent in the genome of each bird, implying that two types of OvoDBs sharing same cysteine motif have already emerged before the species divergence. More importantly, recombinant OvoDBβ mature peptide exerted antibacterial activity against Escherischia coli (CICC23657 strain) in vitro. These results collectively indicated that the putative sequence, namely chicken OvoDBβ, is a function gene with potential antimicrobial property. Discovery and function characterization of novel HDP genes may help us develop novel antimicrobial agents in the future.

Investigating proteins and proteases composing amniotic and allantoic fluids during chicken embryonic development

In amniotes, the amniotic fluid is a significant contributor to fetal development and health. While numerous studies have been conducted in mammalian amniotic fluid, the composition of amniotic and other extraembryonic fluids in avian egg along with their physiological functions remain largely unexplored. In such a context, our objective was to characterize the chicken amniotic fluid (AmF) and allantoic fluid (AlF) properties, protein composition, and some associated functions from day 8 to day 16 of incubation. SDS-PAGE combined to mass spectrometry analysis revealed common and specific proteins to each fluid, suggesting distinct properties and functions. Indeed, major AlF proteins are mostly "egg yolk" proteins involved in lipid, vitamin metabolisms, and metal ion transport, while major AmF proteins resemble those of albumen. Drastic changes in the AmF protein profiles were observed during incubation, when the albumen transfers from day 12 onwards, while few changes were detected for the AlF protein profile. The decreases in osmolality (from 231 to 183 mOsm/kg) and pH (from 8.26 to 7.26) observed in the AlF during incubation are associated with water and electrolytes reallocation for the embryo needs. In contrast, AmF pH value remained stable (≈7.5). Active proteolytic enzymes have been identified in the 2 fluids using gelatin zymography, followed by mass spectrometry analysis for protease identification. A total of 12 proteases was detected in the AlF, compared to 5 in the AmF. We have shown that AlF concentrates proteolytic enzymes assumed to participate in digestive processes: aminopeptidase N, dipeptidyl peptidase-4, meprin A, and 72 kDa type IV collagenase preproprotein. The other proteases identified in both fluids also could have a role in morphogenesis (hepatocyte growth factor activator, suppressor of tumorigenicity 14, astacin-like metalloendopeptidase) and hemostasis (prothrombin and coagulation factor X). Altogether, these data suggest that the roles of chicken AlF and AmF are not merely associated with protection of the embryo and regulation of metabolic disposable wastes, but also they could have more sophisticated roles during embryonic development.

Formation and characterization of peptides in egg white during storage at ambient temperature

Egg white thinning during ambient storage is a well-known phenomenon. The objective of the study was to characterize the formation of peptides <10 kDa in egg white during storage at room temperature. The results indicated that the content of peptides in the egg white fraction of <10 kDa increased gradually. Similar but a faster trend was observed for the fraction of <3 kDa. Gallin, also called ovodefensin (∼7 kDa), was the main component in 10-3 kDa egg white fraction, which rapidly degraded and disappeared at 28 d of storage. Mass spectrometry analysis of <3 kDa fraction identified 6 peptide fragments from ovotransferrin and 11 peptides from ovomucin. Ovodefensin, ovotransferrin and ovomucin are the major innate components of egg defense; thus the degradation of these proteins during storage contributes to egg white thinning and increased susceptibility to bacterial contamination. This study provides the insights on the molecular mechanism of egg deterioration during prolonged ambient storage.

Egg Protein-Derived Bioactive Peptides: Preparation, Efficacy, and Absorption

The hen's egg is an important protein source of human diet. On average one large egg contains ~6g protein, which contributes to ~11% of daily protein intake. As a high-quality protein, egg proteins are well recognized as excellent sources of bioactive peptides. The objectives of this chapter are to introduce generation, bioactivities, and absorption of egg protein-derived bioactive peptides. Research on egg protein-derived bioactive peptides has been progressed during the past decades. Enzymatic hydrolysis is the major technique to prepare bioactive peptides from egg protein. Quantitative structure-activity relationships-aided in silico prediction is increasingly applied as a promising tool for efficient prediction of novel bioactive peptides. A number of bioactive peptides from egg proteins have been characterized for antioxidant, immunomodulatory, antihypertensive, antidiabetic, anticancer, and antimicrobial activities. Egg protein-derived peptides that can improve bone health have been reported as well. However, molecular mechanisms of many peptides are not fully understood. The stability and absorption routes, bioavailability, safety, and production of bioactive peptides await further investigation.

Hydrogen-peroxide-modified egg albumen for transparent and flexible resistive switching memory

Egg albumen is modified by hydrogen peroxide with concentrations of 5%, 10%, 15% and 30% at room temperature. Compared with devices without modification, a memory cell of Ag/10% H₂O₂-egg albumen/indium tin oxide exhibits obviously enhanced resistive switching memory behavior with a resistance ratio of 10⁴, self-healing switching endurance for 900 cycles and a prolonged retention time for a 10⁴ s @ 200 mV reading voltage after being bent 10³ times. The breakage of massive protein chains occurs followed by the recombination of new protein chain networks due to the oxidation of amidogen and the synthesis of disulfide during the hydrogen peroxide modifying egg albumen. Ions such as Fe³⁺, Na⁺, K⁺, which are surrounded by protein chains, are exposed to the outside of protein chains to generate a series of traps during the egg albumen degeneration process. According to the fitting results of the double logarithm I-V curves and the current-sensing atomic force microscopy (CS-AFM) images of the ON and OFF states, the charge transfer from one trap center to its neighboring trap center is responsible for the resistive switching memory phenomena. The results of our work indicate that hydrogen- peroxide-modified egg albumen could open up a new avenue of biomaterial application in nanoelectronic systems.

Flexible bio-memristive devices based on chicken egg albumen:Au@SiO2 core-shell nanoparticle nanocomposites

Flexible bio-memristive (FBM) devices utilizing chicken egg albumen (CEA):Au@SiO₂ core-shell nanoparticle nanocomposites were fabricated on indium-tin-oxide (ITO) coated polyethylene naphthalate (PEN) substrates. Current-voltage (I-V) curves for the Al/CEA:Au@SiO₂ core-shell nanoparticle/ITO/PEN devices showed clockwise current hysteresis behaviors due to the existence of the CEA:Au@SiO₂ core-shell nanoparticle nanocomposites. The endurance number of the ON/OFF switching for the FBM devices was above 10² cycles. An ON/OFF current ratio of 1 × 10⁵ was maintained for retention times longer than 1 × 10⁴ s. The memory characteristics of the FBM devices after bending were similar to those before bending. The memory margin and the stability of FBM devices were enhanced due to the embedded Au@SiO₂ core-shell nanoparticles. The switching mechanisms occurring in the Al/CEA:Au@SiO₂ core-shell nanoparticle/ITO-coated PEN devices are described on the basis of the I-V results and the filament mechanisms.

Protein profiles of hatchery egg shell membrane

BACKGROUND

Eggshells which consist largely of calcareous outer shell and shell membranes, constitute a significant part of poultry hatchery waste. The shell membranes (ESM) not only contain proteins that originate from egg whites but also from the developing embryos and different contaminants of microbial and environmental origins. As feed supplements, during post hatch growth, the hatchery egg shell membranes (HESM) have shown potential for imparting resistance of chickens to endotoxin stress and exert positive health effects. Considering that these effects are mediated by the bioactive proteins and peptides present in the membrane, the objective of the study was to identify the protein profiles of hatchery eggshell membranes (HESM).

METHODS

Hatchery egg shell membranes were extracted with acidified methanol and a guanidine hydrochloride buffer then subjected to reduction/alkylation, and trypsin digestion. The methanol extract was additionally analyzed by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS). The tryptic digests were analyzed by liquid chromatography and tandem mass spectrometry (LC-MS-MS) to identify the proteins.

RESULTS

Our results showed the presence of several proteins that are inherent and abundant in egg white such as, ovalbumin, ovotransferrin, ovocleidin-116, and lysozyme, and several proteins associated with cytoskeletal, cell signaling, antimicrobial, and catalytic functions involving carbohydrate, nucleic acid, and protein metabolisms. There were some blood derived proteins most likely originating from the embryos and several other proteins identified with different aerobic, anaerobic, gram positive, gram negative, soil, and marine bacterial species some commensals and others zoonotic.

CONCLUSION

The variety of bioactive proteins, particularly the cell signaling and enzymatic proteins along with the diverse microbial proteins, make the HESM suitable for nutritional and biological application to improve post hatch immunity of poultry.

In-depth comparative analysis of the chicken eggshell membrane proteome

The avian eggshell membrane (ESM) is stabilized by extensive cross-linkages, making the identification of its protein constituents technically challenging. Herein, we applied various extraction/solubilization conditions followed by proteomic analysis to characterize the protein constituents of ESM derived from the unfertilized chicken eggs. The egg white and eggshell proteomes (including previous published work) were determined and compared to ESM to identify proteins that are relatively or highly specific to ESM. Merging the results from different extraction/solubilization conditions with various proteomes allowed the identification of 472, 225, and 488 proteins in the ESM, egg white, and eggshell proteomes, respectively. Of these, 163 and 124 proteins were relatively or highly specific to ESM, respectively. GO term analysis of the common proteins and ESM unique proteins generated 8 and 9 significantly enriched functional groups, respectively. Different families of proteins that were identified as ESM-specific included collagens, CREMPs, histones, AvBDs, lysyl oxidase-like 2 (LOXL2), and ovocalyxin-36 (OCX36). These proteins serve as a foundation for the mechanically stable ESM that rests upon the egg white compartment and is a physical barrier against pathogen invasion. Overall, our results highlight the structural nature of the ESM constituents that are relevant to various biomedical applications, such as wound healing.

BIOLOGICAL SIGNIFICANCE

The eggshell membranes (ESM) are a highly resilient double-layered fibrous meshwork that is secreted while the forming egg transits a specialized oviduct segment, the white isthmus. The ESM protects against pathogen invasion and provides a platform for nucleation of the calcitic eggshell (ES). ESM is greatly stabilized by the extensive desmosine, isodesmosine and disulfide cross-linkages which make the identification of its protein constituents by standard proteomic approaches technically challenging. Comparative proteomic analyses of ESM, egg white, and ES proteins showed proteins groups that are relatively or highly specific to ESM. These groups of proteins serve as a foundation for the mechanically stable ESM that rests upon the egg white compartment and is a physical barrier against pathogen invasion. These features are essential for eggshell quality and for the prevention of pathogen invasion which reinforce food safety of the table egg.

Genetic Basis of Salmonella Enteritidis Pathogenesis in Chickens

Salmonella Enteritidis (SE) is the predominant cause of the food-borne salmonellosis in humans, in part because this serotype has the unique ability to contaminate chicken eggs without causing discernible illness in the infected birds. Attempts to develop effective vaccines and eradicate SE from chickens are undermined by significant limitations in our current understanding of the genetic basis of pathogenesis of SE in this reservoir host. In this chapter, we summarize the infection kinetics and provide an overview of the current understanding of genetic factors underlying SE infection in the chicken host. We also discuss the important knowledge gaps that, if addressed, will improve our understanding of the complex biology of SE in young chickens and in egg laying hens.

Recent advances in component resolved diagnosis in food allergy

Due to the high prevalence of food allergic diseases globally there are increasing demands in clinical practice for managing IgE-mediated conditions. During the last decade, component resolved diagnostics has been introduced into the field of clinical allergology, providing information that cannot be obtained from extract-based tests. Component resolved data facilitate more precise diagnosis of allergic diseases and identify sensitizations attributable to cross-reactivity. Furthermore it assists risk assessment in clinical practice as sensitization to some allergenic molecules is related to persistence of clinical symptoms and systemic rather than local reactions. The information may also aid the clinician in prescription of oral immunotherapy (OIT) in patients with severe symptoms, and in giving advice on food allergen avoidance or on the need to perform food challenges. The use of allergen components is rapidly evolving and increases our possibility to treat food allergic patients with a more individual approach. Using molecular allergology, we can already now better diagnose, prognose and grade the food allergy. In summary, daily routine molecular allergy diagnostics offers a number of benefits that give us a higher diagnostic precision and allow for better management of the patient.

NMR-based metabolic characterization of chicken tissues and biofluids: a model for avian research

INTRODUCTION

Poultry is one of the most consumed meat in the world and its related industry is always looking for ways to improve animal welfare and productivity. It is therefore essential to understand the metabolic response of the chicken to new feed formulas, various supplements, infections and treatments.

OBJECTIVES

As a basis for future research investigating the impact of diet and infections on chicken's metabolism, we established a high-resolution proton nuclear magnetic resonance (NMR)-based metabolic atlas of the healthy chicken (Gallus gallus).

METHODS

Metabolic extractions were performed prior to 1H-NMR and 2D NMR spectra acquisition on twelve biological matrices: liver, kidney, spleen, plasma, egg yolk and white, colon, caecum, faecal water, ileum, pectoral muscle and brain of 6 chickens. Metabolic profiles were then exhaustively characterized.

RESULTS

Nearly 80 metabolites were identified. A cross-comparison of these matrices was performed to determine metabolic variations between and within each section and highlighted that only eight core metabolites were systematically found in every matrice.

CONCLUSION

This work constitutes a database for future NMR-based metabolomic investigations in relation to avian production and health.

Rapid proteomic responses to a near-lethal heat stress in the salt marsh mussel Geukensia demissa

Acute heat stress perturbs cellular function on a variety of levels, leading to protein dysfunction and aggregation, oxidative stress and loss of metabolic homeostasis. If these challenges are not overcome quickly, the stressed organism can die. To better understand the earliest tissue-level responses to heat stress, we examined the proteomic response of gill from Geukensia demissa, an extremely eurythermal mussel from the temperate intertidal zone of eastern North America. We exposed 15°C-acclimated individuals to an acute near-lethal heat stress (45°C) for 1 h, and collected gill samples from 0 to 24 h of recovery. The changes in protein expression we found reveal a coordinated physiological response to acute heat stress: proteins associated with apoptotic processes were increased in abundance during the stress itself (i.e. at 0 h of recovery), while protein chaperones and foldases increased in abundance soon after (3 h). The greatest number of proteins changed abundance at 6 h; these included oxidative stress proteins and enzymes of energy metabolism. Proteins associated with the cytoskeleton and extracellular matrix also changed in abundance starting at 6 h, providing evidence of cell proliferation, migration and tissue remodeling. By 12 h, the response to acute heat stress was diminishing, with fewer stress and structural proteins changing in abundance. Finally, the proteins with altered abundances identified at 24 h suggest a return to the pre-stress anabolic state.

Egg serpins: The chicken and/or the egg dilemma

Twenty-seven serpins belonging to clade A, B, C, D, E, F, G, H and I serpins are currently referenced in chicken genome databases. Phylogenetic analysis of chicken serpins revealed that ovalbumin (Serpinb14) and its paralogs ovalbumin-related protein Y (Serpinb14b) and ovalbumin-related protein X (Serpinb14c) are found in bird species. These clade B serpins are specifically expressed in reproductive tissues and exported in the egg where they constitute major protein components. These data suggest that these three paralogs have probably appeared in birds to face new environments and ensure the extra-uterine development of an embryo in a shell egg. Twelve other serpins have been identified in the newly produced egg, some of them having a specific distribution in the respective egg structures (eggshell, egg white, vitelline membrane and egg yolk). The physiological role of these egg serpins remain largely unexplored, but there is increasing evidence in literature or by homologies with their mammalian counterparts, that some of them participate in cell proliferation, tissue remodeling and/or angiogenesis associated with folliculogenesis and development of extraembryonic structures, eggshell biomineralization, egg defense and nutrition of the embryo. A better knowledge of the phylogenetic evolution of these 15 serpins in other oviparous species, on their egg distribution, on their regulation during embryonic development (activation/degradation/transfer) and on their functional specificity, is needed to better appreciate their role and their bird-specificity. These review shed light on the multiple possibilities that offer the avian egg model to study the role of serpins in reproduction and developmental biology.

Identification of TENP as the Gene Encoding Chicken Egg White Ovoglobulin G2 and Demonstration of Its High Genetic Variability in Chickens

Ovoglobulin G2 (G2) has long been known as a major protein constituent of chicken egg white. However, little is known about the biochemical properties and biological functions of G2 because the gene encoding G2 has not been identified. Therefore, the identification of the gene encoding G2 and an analysis of its genetic variability is an important step toward the goal of understanding the biological functions of the G2 protein and its utility in poultry production. To identify and characterize the gene encoding G2, we separated G2 from egg white using electrophoresis on a non-denaturing polyacrylamide gel. Two polymorphic forms of G2 protein (G2^A and G2^B), with different mobilities (fast and slow respectively), were detected by staining. The protein band corresponding to G2^B was electro-eluted from the native gel, re-electrophoresed under denaturing conditions and its N-terminal sequence was determined by Edman degradation following transfer onto a membrane. Sequencing of the 47 kDa G2^B band revealed it to be identical to TENP (transiently expressed in neural precursors), also known as BPI fold-containing family B, member 2 (BPIFB2), a protein with strong homology to a bacterial permeability-increasing protein family (BPI) in mammals. Full-length chicken TENP cDNA sequences were determined for 78 individuals across 29 chicken breeds, lines, and populations, and consequently eleven non-synonymous substitutions were detected in the coding region. Of the eleven non-synonymous substitutions, A329G leading to Arg110Gln was completely associated with the noted differential electrophoretic mobility of G2. Specifically G2^B, with a slower mobility is encoded by A329 (Arg110), whereas G2^A, with a faster mobility, is encoded by G329 (Gln110). The sequence data, derived from the coding region, also revealed that the gene encoding G2 demonstrates significant genetic variability across different chicken breeds/lines/populations. These variants, and how they correlate with egg white properties, may allow us to understand further G2’s functions.

Proteomic analysis of egg white heparin-binding proteins: towards the identification of natural antibacterial molecules

The chicken egg resists most environmental microbes suggesting that it potentially contains efficient antimicrobial molecules. Considering that some heparin-binding proteins in mammals are antibacterial, we investigated the presence and the antimicrobial activity of heparin-binding proteins from chicken egg white. Mass spectrometry analysis of the proteins recovered after heparin-affinity chromatography, revealed 20 proteins, including known antimicrobial proteins (avidin, lysozyme, TENP, ovalbumin-related protein X and avian bêta-defensin 11). The antibacterial activity of three new egg candidates (vitelline membrane outer layer protein 1, beta-microseminoprotein-like (LOC101750704) and pleiotrophin) was demonstrated against Listeria monocytogenes and/or Salmonella enterica Enteritidis. We showed that all these molecules share the property to inhibit bacterial growth through their heparin-binding domains. However, vitelline membrane outer layer 1 has additional specific structural features that can contribute to its antimicrobial potential. Moreover, we identified potential supplementary effectors of innate immunity including mucin 5B, E-selectin ligand 1, whey acidic protein 3, peptidyl prolyl isomerase B and retinoic acid receptor responder protein 2. These data support the concept of using heparin affinity combined to mass spectrometry to obtain an overview of the various effectors of innate immunity composing biological milieus, and to identify novel antimicrobial candidates of interest in the race for alternatives to antibiotics.

Identification and comparative proteomic study of quail and duck egg white protein using 2-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry analysis

A proteomic study of egg white proteins from 2 major poultry species, namely quail (Coturnix coturnix) and duck (Anas platyrhynchos), was performed with comparison to those of chicken (Gallus gallus) through 2-dimensional polyacrylamide gel electrophoresis (2-DE) analysis. By using matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF MS/MS), 29 protein spots representing 10 different kinds of proteins as well as 17 protein spots designating 9 proteins were successfully identified in quail and duck egg white, respectively. This report suggested a closer relationship between quail and chicken egg white proteome patterns, whereas the duck egg white protein distribution on the 2-DE map was more distinct. In duck egg white, some well-known major proteins, such as ovomucoid, clusterin, extracellular fatty acid-binding protein precursor (ex-FABP), and prostaglandin D2 synthase (PG D2 synthase), were not detected, while two major protein spots identified as “deleted in malignant brain tumors 1” protein (DMBT1) and vitellogenin-2 were found specific to duck in the corresponding range on the 2-DE gel map. These interspecies diversities may be associated with the egg white protein functions in cell defense or regulating/supporting the embryonic development to adapt to the inhabiting environment or reproduction demand during long-term evolution. The findings of this work will give insight into the advantages involved in the application on egg white proteins from various egg sources, which may present novel beneficial properties in the food industry or related to human health.

Thermal aggregation of hen egg white proteins in the presence of salts

Hen egg white contains more than 40 kinds of proteins with concentrations reaching 100 mg/mL. Highly concentrated protein mixtures are common in the food industry, but the effects of a crowded environment containing salts on protein stability and aggregation have only been investigated using pure protein solutions. Here, we investigated the thermal aggregation of hen egg white protein (EWP) at various concentrations in the presence of inorganic salts by solubility measurements and SDS-PAGE. EWP at 1 mg/mL formed aggregates with increasing temperature above 55 °C; the aggregation temperatures increased in the presence of inorganic salt with the Hofmeister series. Namely, the chaotrope 0.5 M NaSCN completely suppressed the thermal aggregation of 1 mg/mL EWP. As the protein concentration increased, NaSCN unexpectedly enhanced the protein aggregation; the aggregation temperature of 10 and 100 mg/mL EWP solutions were dramatically decreased at 62 and 47 °C, respectively. This decrease in aggregation temperatures due to the chaotrope was described by the excluded volume effect, based on a comparative experiment using Ficoll 70 as a neutral crowder. By contrast, the kosmotrope Na2SO4 did not affect the aggregation temperature at concentrations from 1 to 100 mg/mL EWPs. The unexpected fact that a chaotrope rather enhanced the protein aggregation at high concentration provides new insight into the aggregation phenomena with the Hofmeister effect as well as the crude state of highly concentrated proteins.

Direct matrix-assisted laser desorption ionization time-of-flight mass spectrometric analysis of lysozyme contained in hen egg white

As a natural antibacterial peptide, lysozyme (LZ) is widely used in medicine and the food industry. Despite many years of research on this compound, its new antibacterial properties are still to be determined. The primary aim of this work is to demonstrate the application of the matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometric analysis of LZ directly in hen egg white samples without extraction thereof. The egg white samples were kept over 10 weeks at room temperature and measured every week. The resulting positive and negative ion mass spectra were then compared to determine the intensity of the LZ mass peak. Storage of the egg white for over 10 weeks did not influence the LZ mass peak intensity (both positive and negative). It can be concluded that the LZ concentration in the egg white samples did not vary with time. The effect of the matrix/sample ratio on LZ detection was also examined, and it was found to be different in the case of positive and negative ionization. The mass peaks of LZ oligomeric forms were observed in all mass spectra, so the MALDI method could be used in subsequent studies.

Chicken Egg Shell Membrane Associated Proteins and Peptides

Egg shells are poultry industry byproducts with potential for use in various biological and agricultural applications. We have been interested in the membranes underlying the calcareous shell as a feed supplement, which showed potential to improve immunity and performance of post hatch poultry. Therefore, to determine their protein and peptide profiles, we extracted the egg shell membranes (ESM) from fresh unfertilized eggs with methanol and guanidine hydrochloride (GdHCl) to obtain soluble proteins for analysis by mass spectrometry. The methanol extract was subjected to matrix-assisted laser desorption ionization (MALDI), electrospray ionization (ESI), high-performance reverse phase liquid chromatographic separation (HPLC), and tandem mass spectrometry (MS/MS) to determine its peptide and protein profiles. The GdHCl extract was subjected to ESI-HPLC-MS/MS following trypsin digestion of reduced/alkylated proteins. Nine proteins from the methanol extract and >275 proteins from the GdHCl extract were tentatively identified. The results suggested the presence of several abundant proteins from egg whites, such as ovoalbumin, ovotransferrin, and lysozyme as well as many others associated with antimicrobial, biomechanical, cytoskeletal organizational, cell signaling, and enzyme activities. Collagens, keratin, agrin, and laminin were some of the structural proteins present in the ESM. The methanol-soluble fraction contained several clusterin peptides and defensins, particularly, two isoforms of gallin. The ratios of the two isoforms of gallin differed between the membranes obtained from brown and white eggs. The high abundance of several antimicrobial, immunomodulatory, and other bioactive proteins in the ESM along with its potential to entrap various microbes and antigens may make it a suitable vehicle for oral immunization of post hatch poultry and improve their disease resistance.

Identifying specific proteins involved in eggshell membrane formation using gene expression analysis and bioinformatics

Background

The avian eggshell membranes surround the egg white and provide a structural foundation for calcification of the eggshell which is essential for avian reproduction; moreover, it is also a natural biomaterial with many potential industrial and biomedical applications. Due to the insoluble and stable nature of the eggshell membrane fibres, their formation and protein constituents remain poorly characterized. The purpose of this study was to identify genes encoding eggshell membrane proteins, particularly those responsible for its structural features, by analyzing the transcriptome of the white isthmus segment of the oviduct, which is the specialized region responsible for the fabrication of the membrane fibres.

Results

The Del-Mar 14 K chicken microarray was used to investigate up-regulated expression of transcripts in the white isthmus (WI) compared with the adjacent magnum (Ma) and uterine (Ut) segments of the hen oviduct. Analysis revealed 135 clones hybridizing to over-expressed transcripts (WI/Ma + WI/Ut), and corresponding to 107 NCBI annotated non-redundant Gallus gallus gene IDs. This combined analysis revealed that the structural proteins highly over-expressed in the white isthmus include collagen X (COL10A1), fibrillin-1 (FBN1) and cysteine rich eggshell membrane protein (CREMP). These results validate previous proteomics studies which have identified collagen X (α-1) and CREMP in soluble eggshell extracts. Genes encoding collagen-processing enzymes such as lysyl oxidase homologs 1, 2 and 3 (LOXL1, LOXL2 and LOXL3), prolyl 4 hydroxylase subunit α-2 and beta polypeptide (P4HA2 and P4HB) as well as peptidyl-prolyl cis-trans isomerase C (PPIC) were also over-expressed. Additionally, genes encoding proteins known to regulate disulfide cross-linking, including sulfhydryl oxidase (QSOX1) and thioredoxin (TXN), were identified which suggests that coordinated up-regulation of genes in the white isthmus is associated with eggshell membrane fibre formation.

Conclusions

The present study has identified genes associated with the processing of collagen, other structural proteins, and disulfide-mediated cross-linking during eggshell membrane formation in the white isthmus. Identification of these genes will provide new insight into eggshell membrane structure and mechanisms of formation that will assist in the development of selection strategies to improve eggshell quality and food safety of the table egg.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2013-3) contains supplementary material, which is available to authorized users.

Egg white versus Salmonella Enteritidis! A harsh medium meets a resilient pathogen

Salmonella enterica serovar Enteritidis is the prevalent egg-product-related food-borne pathogen. The egg-contamination capacity of S. Enteritidis includes its exceptional survival capability within the harsh conditions provided by egg white. Egg white proteins, such as lysozyme and ovotransferrin, are well known to play important roles in defence against bacterial invaders. Indeed, several additional minor proteins and peptides have recently been found to play known or potential roles in protection against bacterial contamination. However, although such antibacterial proteins are well studied, little is known about their efficacy under the environmental conditions prevalent in egg white. Thus, the influence of factors such as temperature, alkalinity, nutrient restriction, viscosity and cooperative interactions on the activities of antibacterial proteins in egg white remains unclear. This review critically assesses the available evidence on the antimicrobial components of egg white. In addition, mechanisms employed by S. Enteritidis to resist egg white exposure are also considered along with various genetic studies that have shed light upon egg white resistance systems. We also consider how multiple, antibacterial proteins operate in association with specific environmental factors within egg white to generate a lethal protective cocktail that preserves sterility.

Global Proteomic Analysis of Functional Compartments in Immature Avian Follicles Using Laser Microdissection Coupled to LC-MS/MS

Laser microdissection (LMD) was utilized for the separation of the yolk, follicular wall (granulosa and theca), and surrounding stromal cells of small white follicles (SWF) obtained from reproductively active domestic fowl. Herein, we provide an in situ proteomics-based approach to studying follicular development through the use of LMD and mass spectrometry. This study resulted in a total of 2889 proteins identified from the three specific isolated compartments. White yolk from the smallest avian follicles resulted in the identification of 1984 proteins, while isolated follicular wall and ovarian stroma yielded 2470 and 2456 proteins, respectively. GO annotations highlighted the functional differences between the compartments. Among the three compartments examined, the relative abundance of vitellogenins, steroidogenic enzymes, anti-Mullerian hormone, transcription factors, and proteins involved in retinoic acid receptors/retinoic acid synthesis, transcription factors, and cell surface receptors such as EGFR and their associated signaling pathways reflected known cellular function of the ovary. This study has provided a global proteome for SWF, white yolk, and ovarian stroma of the avian ovary that can be used as a baseline for future studies and verifies that the coupling of LMD with proteomic analysis can be used to evaluate proteins from small, physiologically functional compartments of complex tissue.

Extraction and identification of membrane proteins from black widow spider eggs

The eggs of oviparous animals are storehouses of maternal proteins required for embryonic development. Identification and molecular characterization of such proteins will provide much insight into the regulation of embryonic development. We previously analyzed soluble proteins in the eggs of the black widow spider (Latrodectus tredecimguttatus), and report here on the extraction and mass spectrometric identification of the egg membrane proteins. Comparison of different lysis solutions indicated that the highest extraction of the membrane proteins was achieved with 3%-4% sodium laurate in 40 mmol/L Tris-HCl buffer containing 4% CHAPS and 2% DTT (pH 7.4). SDS-PAGE combined with nLC-MS/MS identified 39 proteins with membrane-localization annotation, including those with structural, catalytic, and regulatory activities. Nearly half of the identified membrane proteins were metabolic enzymes involved in various cellular processes, particularly energy metabolism and biosynthesis, suggesting that relevant metabolic processes were active during the embryonic development of the eggs. Several identified cell membrane proteins were involved in the special structure formation and function of the egg cell membranes. The present proteomic analysis of the egg membrane proteins provides new insight into the molecular mechanisms of spider embryonic development.

In-depth LC-MS/MS analysis of the chicken ovarian cancer proteome reveals conserved and novel differentially regulated proteins in humans

Ovarian cancer (OVC) remains the most lethal gynecological malignancy in the world due to the combined lack of early-stage diagnostics and effective therapeutic strategies. The development and application of advanced proteomics technology and new experimental models has created unique opportunities for translational studies. In this study, we investigated the ovarian cancer proteome of the chicken, an emerging experimental model of OVC that develops ovarian tumors spontaneously. Matched plasma, ovary, and oviduct tissue biospecimens derived from healthy, early-stage OVC, and late-stage OVC birds were quantitatively characterized by label-free proteomics. Over 2600 proteins were identified in this study, 348 of which were differentially expressed by more than twofold (p ≤ 0.05) in early- and late-stage ovarian tumor tissue specimens relative to healthy ovarian tissues. Several of the 348 proteins are known to be differentially regulated in human cancers including B2M, CLDN3, EPCAM, PIGR, S100A6, S100A9, S100A11, and TPD52. Of particular interest was ovostatin 2 (OVOS2), a novel 165-kDa protease inhibitor found to be strongly upregulated in chicken ovarian tumors (p = 0.0005) and matched plasma (p = 0.003). Indeed, RT-quantitative PCR and Western blot analysis demonstrated that OVOS2 mRNA and protein were also upregulated in multiple human OVC cell lines compared to normal ovarian epithelia (NOE) cells and immunohistochemical staining confirmed overexpression of OVOS2 in primary human ovarian cancers relative to non-cancerous tissues. Collectively, these data provide the first evidence for involvement of OVOS2 in the pathogenesis of both chicken and human ovarian cancer.

The Family Secrets of Avian Egg-Specific Ovalbumin and Its Related Proteins Y and X

The ovalbumin gene family in Gallus gallus is composed of three homologous genes located within a 46 kb locus on chromosome 2: ovalbumin, ovalbumin-related protein Y (OVAY), and ovalbumin-related protein X (OVAX) genes. The expression of these genes in hen oviduct is under estrogen control, but their relative hormonal responsiveness and subsequent protein concentration in egg, is distinctive. Interestingly, all three proteins lack the classical signal peptide for secretion. Ovalbumin, OVAX, and OVAY belong to the serine protease inhibitor (serpin) family whose members share a common tertiary structure. Ovalbumin and OVAX are one of the few members of this family that do not express any protease inhibition activity whereas OVAY has been predicted to be inhibitory, by comparison with the consensus sequence for inhibitory serpins. In contrast to ovalbumin and OVAY, OVAX interacts with heparin, a negatively charged glycosaminoglycan, via a positively charged domain exposed at the surface of the molecule. Ovalbumin is the major egg white protein and might be a source of amino acids for the developing embryo. The physiological function of OVAY is not known, but recent data have revealed a possible role of this protein in early embryonic development. Considering the antibacterial activities of OVAX, this protein might play a role in egg defense. This review sheds light on the expression, biochemistry, and structural specificities of these three highly similar paralogs. It gives new clues in favor of diverging functions, which are likely to have arisen by duplication events from a common ancestral gene.

The impact of fertilization on the chicken egg yolk plasma and granule proteome 24 hours post-lay at room temperature: capitalizing on high-pH/low-pH reverse phase chromatography in conjunction with tandem mass tag (TMT) technology

Chicken egg yolk is a rich source of nutrients providing high quality proteins, vitamins, minerals, carotenoids and antioxidants. Chicken egg yolk, recovered from whole egg within 24 hours post-lay has been utilized as a starting material in the preparation of a dietary supplement that has been demonstrated to lead to gains in muscle mass in a human clinical study. Further, an oil derived from chicken egg yolk has been utilized as a topical agent to treat third degree burn injury. The molecular changes that take place in fertilized, chicken egg yolk during the first 24 hours post-lay are not well understood. By studying how the protein composition of egg yolk varies with fertility status, one can utilize this knowledge to develop egg yolk-based products that have been optimized for specific applications. In this study, a direct quantitative comparison was made between the proteome of fertilized chicken egg yolk and the proteome of unfertilized chicken egg yolk, both maintained at 20 °C and analyzed within 24 hours post-lay. Egg yolk proteins from each fertility state were digested with trypsin, labeled with distinct chemical labels (tandem mass tag reagents) and then combined in a 1 : 1 ratio. A TMT-labeled tryptic digest derived from chicken egg yolk proteins (fertilized and unfertilized) was separated using high-pH/low-pH reverse-phase chromatography and analyzed using mass spectrometry. 225 protein identifications were made from this TMT-labeled tryptic digest based on a minimum of 2 unique peptides observed per protein. 9 proteins increased in abundance in fertilized egg yolk relative to unfertilized egg yolk and 9 proteins decreased in abundance in fertilized egg yolk relative to unfertilized egg yolk. Some proteins that increased in abundance in fertilized egg yolk play an important role in angiogenesis (pleiotrophin, histidine rich glycoprotein) and defense against pathogens (mannose-binding lectin, β-defensin 11, serum amyloid P-component, ovostatin). Based on this study, fertilized chicken egg yolk may be more useful as a starting material relative to unfertilized chicken egg yolk for the purpose of enriching or isolating proteins with pro-angiogenic and anti-microbial properties.

Nonvolatile bio-memristor fabricated with egg albumen film

This study demonstrates the fabrication and characterization of chicken egg albumen-based bio-memristors. By introducing egg albumen as an insulator to fabricate memristor devices comprising a metal/insulator/metal sandwich structure, significant bipolar resistive switching behavior can be observed. The 1/f noise characteristics of the albumen devices were measured, and results suggested that their memory behavior results from the formation and rupture of conductive filaments. Oxygen diffusion and electrochemical redox reaction of metal ions under a sufficiently large electric field are the principal physical mechanisms of the formation and rupture of conductive filaments; these mechanisms were observed by analysis of the time-of-flight secondary ion mass spectrometry (TOF-SIMS) and resistance-temperature (R-T) measurement results. The switching property of the devices remarkably improved by heat-denaturation of proteins; reliable switching endurance of over 500 cycles accompanied by an on/off current ratio (Ion/off) of higher than 10(3) were also observed. Both resistance states could be maintained for a suitably long time (>10(4) s). Taking the results together, the present study reveals for the first time that chicken egg albumen is a promising material for nonvolatile memory applications.

Nutritional effects of egg shell membrane supplements on chicken performance and immunity

Eggshell membranes (ESM) contain a variety of proteins and peptides which help in the development of embryo and provide protection to it. Many of the peptides and proteins associated with ESM have antimicrobial, immune-modulatory, and adjuvant properties. We hypothesized that the membrane byproducts from egg, provided as posthatch nutritional supplements to chickens, may improve their performance and immunity. To explore its effect, we fed 3 groups of broiler chicks with feed containing 0, 0.2, and 0.4% ESM from d 1 posthatch through 14 d and regular feed thereafter. The birds were individually weighed at the onset of the study and at weekly intervals until the termination at third wk when they were bled and euthanized. The relative weights of liver, spleen, bursa, and heart, hematology profiles, and clinical chemistry variables including serum IgM, IgG, and corticosterone concentrations were measured. The chickens in the ESM treated groups showed a statistically significant increase in BW with no impact on relative organ weights. Compared with controls, the WBC and lymphocyte percentage increased in chickens fed 0.4% ESM whereas the monocyte percentage decreased at both levels of ESM. Except for the serum protein which increased in ESM fed birds no other metabolic clinical chemistry variables showed any significant change. Both IgM and IgG(Y) levels were elevated and corticosterone levels reduced in chickens fed ESM supplemented diets. Our results suggest that ESM supplements during the early phases of growth may improve immunity and stress variables, and enhance their growth performance without any detrimental effect on other physiological parameters.

Differential abundance of egg white proteins in laying hens treated with corticosterone

Stressful environments can affect not only egg production and quality but also gene and protein abundance in the ovary and oviduct in laying hens. The oviductal magnum of laying hens is the organ responsible for the synthesis and secretion of egg white proteins. The objective of this study was to investigate the effects of dietary corticosterone as a stress model on the abundance of proteins in the egg white and of mRNA and proteins in the magnum in laying hens. After a 14-day acclimation, 40 laying hens were divided into two groups which were provided for the next 14 days with either control (Control) or corticosterone (Stress) diet containing at 30 mg/kg. Corticosterone treatment resulted in increased feed intake (P ≤ 0.05) and decreased egg production. Two-dimensional electrophoresis (2DE) with MALDI-TOF/TOF MS/MS using eggs obtained on days 0 and 5 revealed differential abundance of egg white proteins by Stress: transiently expressed in neural precursors (TENP), hemopexin (HPX), IgY-Fcυ3-4, and extracellular fatty acid-binding protein (Ex-FABP) were decreased while ovoinhibitor and ovalbumin-related protein X (OVAX) were increased on days 5 vs 0 (P ≤ 0.05). Expression of mRNAs and proteins was also significantly modulated in the magnum of hens in Stress on day 14 (P ≤ 0.05). In conclusion, the current study provides the first evidence showing that dietary corticosterone modulates protein abundance in the egg white in laying hens, and it suggests that environmental stress can differentially modify expression of egg white proteins in laying hens.

Eggshell membrane biomaterial as a platform for applications in materials science

Eggshell membrane (ESM) is a unique biomaterial, which is generally considered as waste. However, it has extraordinary properties which can be utilized in various fields and its potential applications are therefore now being widely studied. The first part of this review focuses on the chemical composition and morphology of ESM. The main areas of ESM application are discussed in the second part. These applications include its utilization as a biotemplate for the synthesis of nanoparticles; as a sorbent of heavy metals, organics, dyes, sulfonates and fluorides; as the main component of biosensors; in medicine; and various other applications. For each area of interest, a detailed literature survey is given.