BIOL 103 Lecture Notes - Lecture 16: Santa Barbara City College, Dolichol, Golgi Apparatus
Document Summary
Post-translational modifications of protein in golgi: addition of polysaccharides. The enzymes that carry out these reactions are located in the lumen of the er and the golgi and not in cytosol, meaning proteins being glycosylated are likely bound for secretion and are membrane proteins. An oligosaccharide tree consisting of n-acetyl glucosamine, several mannose, and a few glucose residues is transferred from a lipid known as dolichol. The dolichol with the oligosaccharide attached is assembled on the cytosolic side of the er membrane and then flipped to the lumen (cisternal) side of the membrane by a flippase. After the tree is transferred, the dolichol is free to be reused by adding a new oligosaccharide tree to it for another round of glycosylation. The tree attaches to an asparagine residue through its free amino group. The asn residue is part of a specific amino acid target sequence recognized by the enzyme involved.
