Glycosylation of proteins in the ER is associated with which of the following molecules or responses?

• A. Unfolded protein response
• B. Protein disulfide isomerase
• C. Glycosylphosphatidyl-inositol (GPI) anchor
• D. Dolichol

Answer: (D)

Verified step by step guidance

1. Understand that glycosylation is the process of adding carbohydrate groups to proteins, which is crucial for proper protein folding and stability.
2. Recognize that in the endoplasmic reticulum (ER), N-linked glycosylation is a common type of glycosylation where oligosaccharides are attached to the nitrogen atom of asparagine side chains in proteins.
3. Identify that dolichol is a lipid molecule that plays a key role in the N-linked glycosylation process. It acts as a carrier for the oligosaccharide precursor that is transferred to the nascent protein.
4. Recall that the oligosaccharide is initially assembled on the dolichol phosphate molecule on the cytoplasmic side of the ER membrane before being flipped into the lumen of the ER.
5. Conclude that dolichol is directly associated with the glycosylation of proteins in the ER, as it is essential for the initial steps of N-linked glycosylation.