Which statement about glycosylation in expression systems is true?

• A. Glycosylation is a post-translational modification commonly achieved in prokaryotes.
• B. Glycosylation is a post-translational modification common in prokaryotes.
• C. Glycosylation is a post-translational modification that does not affect protein function.
• D. Glycosylation is a post-translational modification that is commonly found in eukaryotes but typically absent in bacteria.

Answer: (C)

Glycosylation is a post-translational modification that is a hallmark of many eukaryotic proteins. It often plays a crucial role in proper folding, stability, trafficking, and functional activity of the protein. In typical expression systems, glycosylation is a feature of eukaryotic hosts (like yeast, insect, or mammalian cells) and is not a standard, common modification in bacterial systems. There are rare bacterial glycosylation pathways, but they differ from the common eukaryotic types and are not routinely used to produce glycoproteins in bacteria.

So, the statement that best fits general understanding is that glycosylation is a post-translational modification found in eukaryotes and typically absent in bacteria. This is consistent with how expression systems are chosen when glycosylation is important for the protein’s function. Glycosylation does affect protein function—contrary to the option that claims it does not.