Cell biology help Glycoproteins are large macromolecules that are found on the c

Question

Cell biology help

Glycoproteins are large macromolecules that are found on the cell surface. They are glycosylated with oligosaccharides in the ER and then translocated to the cell surface. On the cell surface, these glycoproteins play important role in cell-cell recognition. For example, our immune system can recognize foreign (e.g., bacterial glycoprotein) glycoproteins and raise immuneresponse against the bacteria whenever it enters our system.

You are studying a transmembrane glycoprotein, GP1, on a pathogenic bacteria that is recognized by human immune cells. Now you want to make this glycoprotein in the lab by recombinant technology and then add the branched 14-sugar oligosaccharide to the only asparagine residue of the Asn-X-Ser sequence found on your GP1 (Figure 1). After making this recombinant GP1 you exposed this to human immune cells. Unfortunately, immune cells do not seem to recognize this recombinant GP1. Which of the following statements is a likely explanation for this problem and WHY? Explain your answer.

a) The oligosaccharide should have been added to the serine instead of the asparagine.

b) The oligosaccharide should have been added one sugar at a time.

c) The oligosaccharide needs to be further modified before it is mature.

d) The oligosaccharide needs a disulfide bond.

Explanation / Answer

The correct option is c the oligosaccharide needs to be further modified before it is mature. This is because the oligosaccharides are modified by the enzymes in the ER and the Golgi before its insertion into the plasma membrane. It lacks the modifications due to which it is not recognized by the immune cells.

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