Epidermal growth factor (EGF) domains are posttranslationally modified with unique
O-linked glycans. The classical types of
O-glycans on EGF domains are
O-fucose and
O-glucose glycans, found on many plasma glycoproteins and signaling molecules, whose biological functions have been demonstrated especially in the context of the Notch signaling pathway. We recently discovered
O-GlcNAc modification as a new modification of the EGF domain that occurs on the conserved Ser/Thr residue located between the fifth and sixth cysteine residues within the EGF domains of Notch receptors in Drosophila. Isolation of the unidentified enzyme responsible for the extracellular
O-GlcNAcylation and characterization of the
O-GlcNAc transferase gene will reveal the new biological roles for
O-GlcNAcylation in secreted and membrane glycoproteins and the extracellular environment.
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