Comprehensive O-GlcNAc glycoproteomics on NOTCH1 EGF repeats refined the sequons for O-GlcNAcylation and uncovered unique Lewis X epitopes in mammals

This study performed the comprehensive mass spectrometric analyses of O-GlcNAc glycans on NOTCH1 in mammalian cultured cells. The results indicated that the O-GlcNAcylation occurs only a subset of EGF repeats harboring putative O-GlcNAcylation sites, refining the sequons for extracellular O-GlcNAcylation in mammals. Moreover, novel structures with fucosylated O-GlcNAc glycans were identified and the similar structure was detected on O-fucose glycans, extending the view of structural diversity of functional Notch O-glycans.