Endoplasmic reticulum core protein synthesis

The synthesis of the core proteins occurs in the endoplasmic reticulum, and formation of at least some of the above linkages also occurs there. Most of the later steps in the biosynthesis of GAG chains and their subsequent modifications occur in the Golgi apparatus. 

The synthesis of glycosylphosphatidylinositol (GPI) anchors of proteins, including Thy-1 of neurons and lymphocytes, is primarily carried out within the lumen of the rough endoplasmic reticulum. The anchor consists of a phosphatidylinositol-glucosamine-mannosey-ethanolamine phosphate core that is linked to the a-carboxyl of the carboxyterminal amino acid of a protein (Figure 16-12). This addition takes place within minutes of... 

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