Dol= Dolichol .=Mannosc Acetylglucosamine A-Glucose Rough ER 3 cIs golgi 3a 了 IManIg GicNAclz (Glci/ManlgIGlcNAch2
3. The initial steps of protein glycosylation(N-linkage) ar carried out in the er The common core segment of consisting of 14 sugar residues(2GICNAC, 3 Glc and 9 Mannose) of each carbohydrate chain put together independently on a lipid carrier(dolichol phosphate). This core oligosaccharide then transferred, as a block, to specific asparagine residues in the consensus sequence Asn-X-Ser/Thr of the polypeptide being translocated into the ER lumen by oligosaccharyltransferase for the construction of the core oligosaccharide Modification of the core oligosaccharide begins in the ER with the removal of the terminal glucose residues by glycosidases. Four sugar residues(3 Glucose and 1 mannose) are removed while the protein linking the core oligosaccharide([Man]8IGICNAc]2 is still within the ER and the protein is further modified after being transported to the GC
3. The initial steps of protein glycosylation (N-linkage) are carried out in the ER The common core segment of consisting of 14 sugar residues (2GlcNAc, 3 Glc and 9 Mannose) of each carbohydrate chain put together independntly on a lipid carrier (dolichol phosphate). This core oligosaccharide then transferred, as a block, to specific asparagine residues in the consensus sequence Asn-X-Ser/Thr of the polypeptide being translocated into the ER lumen by oligosaccharyltransferase for the construction of the core oligosaccharide. Modification of the core oligosaccharide begins in the ER with the removal of the terminal glucose residues by glycosidases. Four sugar residues (3 Glucose and 1 mannose) are removed while the protein linking the core oligosaccharide ([Man]8[GlcNAc]2 is still within the ER and the protein is further modified after being transported to the GC
3. Modification to N-linked oligosaccharides are completed in the Golgi complex The most clearly defined function of Golgi complex is the assembly of the carbohydrates. Golgi complex is the site where the assembly of the oligosaccharides attached glycoproteins and glycolipids, including both the further removal and addition of carbohydrate residues are completed, depending on the protein. Added sugar residues are transferred to the oligosaccharides, one at a time by specific glycosyltransferase, as they pass through the gC from cis- medial- to trans-cisternae 4. The GC is also the site of synthesis of most of a cells complex polysaccharides such as the glycoaminoglycans (GAGS) found in ECM of anomal cells and the pectins and hemicellulose found in the cell walls of plants
3. Modification to N-linked oligosaccharides are completed in the Goligi complex The most clearly defined function of Golgi complex is the assembly of the carbohydrates. Golgi complex is the site where the assembly of the oligosaccharides attached glycoproteins and glycolipids, including both the further removal and addition of carbohydrate residues are completed, depending on the protein. Added sugar residues are transferred to the oligosaccharides, one at a time by specific glycosyltransferase, as they pass through the GC from cis-, medial-, to trans-cisternae. 4. The GC is also the site of synthesis of most of a cell’s complex polysaccharides such as the glycoaminoglycans (GAGs) found in ECM of anomal cells and the pectins and hemicellulose found in the cell walls of plants
a-mannosidase GlcNAC- GIcNAC fucosyl Sialyl- transferase I transferase‖l galactosyl transferase transfer ase cis golgi cis golgi medial golgi medial Golgi medial Golgi trans Go trans golgi medial Golg trans golgi O N-Acetylglucosamine Mannose A Galactose Sialic acid ( Fucose Figure 8. 22 Steps in the glycosylation of a mammalian- are subsequently removed, while a variety of sugars(N-acety Hokedeligosaccharidein the gol conley followrin th
Transport vesicle from ER Golgi s (Man)atGIcNAC)z MAnis(GICNAC)2 2 3 45 △edsa UDP- T UDP- YGDP△ (GlcNAckManIs(GIcNAcl2 IManIsIGIcNAc)? Exit UDP CMP M-acetvlglucosamine e- Galactose Mannose FI uIcose Glucose A-acetyIneuraminic acid