Figure 2.

Schematic structure of heavily glycosylated glycoproteins. (a) Proteoglycans are transmembrane glycoproteins that consist of a core protein decorated with glycosaminoglycan (GAG) chains. In glypicans, the protein core is stabilized by disulphide bridges and linked to the cell membrane via GPI-anchors. Both glypicans and syndecans contain serine-linked heparin sulphate and chondroitin sulphate GAGs at both sides of the protein (here only depicted on one side), classifying them as HSPGs. (b) Mucins are high-molecular weight proteins that are extensively decorated with mucin-type O-Glycans, schematically illustrated here by the sTn epitope. Mucins are subdivided into transmembrane (MUC1, MUC3, MUC4, MUC12, MUC13, MUC16, and MUC17) and secreted mucins (MUC2, MUC5AC, MUC5B, and MUC6).