N-glycoproteomic analysis of duck egg yolk proteins: Implications for biofunctions and evolution.

Egg yolk contains multifunctional glycoproteins, which modulate embryogenesis and indicate species-specific adaptation. Here, we conducted an N-glycoproteomic study of duck egg yolk (DEY) and identified 359 N-glycosites corresponding to 113 glycoproteins. The comparison of DEY N-glycoproteins with those of chicken egg yolk (CEY) revealed a higher N-glycosylation level in DEY proteins, suggesting a biological adaption to meet the requirements for embryo development by modulating protein structure and binding ability, including immune response and ligand transport. This variation may be correlated to the strong resistance to the influenza virus disease of duck. A large set of corresponding glycoproteins between DEY and CEY were detected with similar molecular functions, which suggested a relatively lower evolution speed of avian egg yolk proteins than that of egg white proteins.