Title : Crystal structure of N-glycosylated human
glypican-1 core
protein : structure of two loops evolutionarily conserved in vertebrate
glypican-1
Abstract :
- Glypicans are a family of cell-surface proteoglycans that regulate Wnt, hedgehog, bone morphogenetic protein , and fibroblast growth factor signaling
- Loss-of-function mutations in glypican core proteins and in glycosaminoglycan-synthesizing enzymes have revealed that glypican core proteins and their glycosaminoglycan chains are important in shaping animal development
- Glypican core proteins consist of a stable α-helical domain containing 14 conserved Cys residues followed by a glycosaminoglycan attachment domain that becomes exclusively substituted with heparan sulfate (HS) and presumably adopts a random coil conformation
- Removal of the α-helical domain results in almost exclusive addition of the glycosaminoglycan chondroitin sulfate , suggesting that factors in the α-helical domain promote assembly of HS
- Glypican-1 is involved in brain development and is one of six members of the vertebrate family of glypicans
- We expressed and crystallized N-glycosylated human glypican-1 lacking HS and N-glycosylated glypican-1 lacking the HS attachment domain
- The crystal structure of glypican-1 was solved using crystals of selenomethionine-labeled glypican-1 core protein lacking the HS domain
- No additional electron density was observed for crystals of glypican-1 containing the HS attachment domain , and CD spectra of the two protein species were highly similar
- The crystal structure of N-glycosylated human glypican-1 core protein at 2.5 Å, the first crystal structure of a vertebrate glypican, reveals the complete disulfide bond arrangement of the conserved Cys residues , and it also extends the structural knowledge of glypicans for one α-helix and two long loops
- Importantly, the loops are evolutionarily conserved in vertebrate glypican-1 , and one of them is involved in glycosaminoglycan class determination