Glypican

The glypican family of Heparan Sulfate proteoglycans are anchored to the cell-surface via a covalent linkage to glycosylphosphatidylinositol (GPI). Six glypican family members have been identified in vertebrates, two in Drosophila and one in C. elegans.

Structure
All glypicans contain an N-terminal signal peptide and a hydrophobic domain in their C-terminal region, required for attachment of the GPI anchor. The amino acid sequences of the six vertebrate glypican family members vary from being 17% to 63% identical. The location of 14 cysteine amino acids is conserved between the glypicans, suggesting the existence of a highly similar three-dimensional structure. The attachment of Heparan sulfate (HS) glycosaminoglycan chains to glypicans is restricted to the last 50 amino acids in the C-terminus, placing glypican HS chains close to the cell membrane.