interspecies comparison of GNA binding proteins

A very common co-translational modification in multicellular organisms is the addition of carbohydrate structures called glycans to the peptide backbone. This important protein modification is called protein glycosylation. In this report, the diversity in protein glycosylation between insect species covering a wide phylogenetic distance was analyzed. Based on previous data of the glycan profile from the fruit fly (Drosophila melanogaster), the oligomannose N- glycan binding snowdrop lectin (Galanthus nivalis agglutinin, GNA) was selected for affinity chromatography of glycoproteins. The insect species that were used in this study were the flour beetle (Tribolium castaneum), the silkworm (Bombyx mori), the honey bee (Apis mellifera), the fruit fly (D. melanogaster) and the pea aphid (Acyrthosiphon pisum). To identify and characterize the purified glycoproteins, LC-MS/MS analysis was performed. For all insect species, it was demonstrated that glycoproteins are involved in a broad range of biological processes and molecular functions. However, major differences between insect species were observed for particular glycosylated proteins. This finding was reflected by differences in the relative abundance of particular proteins for certain biological processes or molecular functions. Besides the abundant presence of oligomannose N-glycans on insect glycoproteins, we also showed that O-mannosylation events occur more frequently than currently anticipated.