Antimicrobial Proteins and Peptides in Avian Eggshell: Structural Diversity and Potential Roles in Biomineralization

Abstract

The calcitic avian eggshell provides physical protection for the embryo during its development, but also regulates water and gaseous exchange, and is a calcium source for bone mineralization. The calcified eggshell has been extensively investigated in the chicken. It is characterized by an inventory of more than 900 matrix proteins. In addition to proteins involved in shell mineralization and regulation of its microstructure, the shell also contains numerous antimicrobial proteins and peptides (AMPPs) including lectin-like proteins, Bacterial Permeability Increasing/Lipopolysaccharide Binding Protein/PLUNC family proteins, defensins, antiproteases, and chelators, which contribute to the innate immune protection of the egg. In parallel, some of these proteins are thought to be crucial determinants of the eggshell texture and its resulting mechanical properties. During the progressive solubilization of the inner mineralized eggshell during embryonic development (to provide calcium to the embryo), some antimicrobials may be released simultaneously to reinforce egg defense and protect the egg from contamination by external pathogens, through a weakened eggshell. This review provides a comprehensive overview of the diversity of avian eggshell AMPPs, their three-dimensional structures and their mechanism of antimicrobial activity. The published chicken eggshell proteome databases are integrated for a comprehensive inventory of its AMPPs. Their biochemical features, potential dual function as antimicrobials and as regulators of eggshell biomineralization, and their phylogenetic evolution will be described and discussed with regard to their three-dimensional structural characteristics. Finally, the repertoire of chicken eggshell AMPPs are compared to orthologs identified in other avian and non-avian eggshells. This approach sheds light on the similarities and differences exhibited by AMPPs, depending on bird species, and leads to a better understanding of their sequential or dual role in biomineralization and innate immunity.

Comparative N-Glycoproteomic Investigation of Eggshell Cuticle and Mineralized Layer Proteins

“…45,46 Considering the glycosylation of OVT in various parts of the egg along with its antimicrobial properties, the Nglycan chain may play an important role in the structural stability and function of OVT. 47,48 Two possible mechanisms by which glycosylation increased the antibacterial activity of OVT are an increased ratio of β-sheets and β-turns, resulting in a stabler structure, and reduced hydrophobic residue contents, thereby increasing its solubility. 44 Aside from competing with bacteria for iron, OVT elicits additional antimicrobial properties by interacting with bacterial cell membranes.…”

“…Therefore, OVT is one of the antimicrobial components in the ECL . Moreover, previous studies that employed nuclear magnetic resonance spectroscopy demonstrated that OVT-linked carbohydrate chains do not contain galactose and sialic acid, which is distinct from the glycosylation of serum transferrin. , Considering the glycosylation of OVT in various parts of the egg along with its antimicrobial properties, the N -glycan chain may play an important role in the structural stability and function of OVT. , Two possible mechanisms by which glycosylation increased the antibacterial activity of OVT are an increased ratio of β-sheets and β-turns, resulting in a stabler structure, and reduced hydrophobic residue contents, thereby increasing its solubility . Aside from competing with bacteria for iron, OVT elicits additional antimicrobial properties by interacting with bacterial cell membranes. ,, …”

TMT-based quantitative proteomic analysis reveals eggshell matrix protein changes correlated with eggshell quality in Jing Tint 6 laying hens of different ages

“…( Marie et al, 2015b ). Lysozyme C, in addition to its antibacterial defense role, has been suggested to play a role in eggshell biomineralization ( Moreau et al, 2022 ). Under in vitro conditions, high concentrations of LYZ have been shown to alter crystal morphology ( Hincke et al, 2000 ).…”

Combined Potential of Quarry Waste Fines and Eggshells for the Hydrothermal Synthesis of Tobermorite at Varying Cement Content

“…These results are supported by the literature stating that the decomposition of volatile materials such as moisture or surface water and organic compounds occurs at the range of 30 • C to 400 • C. The loss of organic compounds is primarily due to the removal of a membrane adhered to the eggshell. This membrane consists of carbohydrates and proteins which are rich in organic matter [65][66][67]. Another endothermic fluctuation along with a sharp drop in mass of approximately −24.76 mg is observed at 849.82 • C which indicates the decomposition of CaCO 3 .…”

“…The loss of organic compounds is primarily due to the removal of a membrane adhered to the eggshell. This membrane consists of carbohydrates and proteins which are rich in organic matter [65][66][67]. Another endothermic fluctuation along with a sharp drop in mass of approximately −24.76 mg is observed at 849.82 °C which indicates the decomposition of CaCO3.…”