Egg proteins: what are their functions?

The principal functions so far attributed to egg proteins are: (i) provision of nutrient for the developing embryo; (ii) protection of the egg from microbial attack; and (iii) transport of nutrients into the developing embryo. All the proteins contribute to the nutrient role in the form of the amino acid residues they contain. Some also contribute to the phosphate reserves. Protection is provided by a variety of means, including the physical barrier of albumen with its high viscosity, and the chemical barriers in the form of protease inhibitors, nutrient sequesters, a lytic enzyme, and antibodies. Various proteins are involved in nutrient uptake, either by acting as carriers or in the form of membrane receptors.