Question

What happens to a newly synthesized glycoprotein after the binding of calnexin or calreticulin to help the protein correctly complete its folding?

1) When the glycoprotein's folding is correctly completed, the remaining glucose on its oligosaccharide chain is eventually reduced and the glycoprotein is released from the chaperone.
2) The oligosaccharide chain is totally degraded.
3) Nothing happens.
4) When the glycoprotein's folding is correctly completed, the remaining glucose on its oligosaccharide chain is eventually removed enzymatically and the glycoprotein is released from the chaperone.
5) The oligosaccharide chain is totally degraded.

Answer 1

After binding to a newly synthesized glycoprotein, calnexin or calreticulin assist in completing its folding correctly, preventing premature release from the endoplasmic reticulum. These chaperones promote proper folding by providing a favorable environment and facilitating the formation of disulfide bonds.

Step-by-step explanation:

After the binding of calnexin or calreticulin to a newly synthesized glycoprotein in the endoplasmic reticulum, these chaperones assist the protein in correctly completing its folding. Calnexin and calreticulin are both lectin chaperones that recognize the specific carbohydrate structures on the glycoprotein. They have the ability to bind to the underglycosylated protein and prevent its premature release from the endoplasmic reticulum.

Once bound, calnexin or calreticulin promote the proper folding of the glycoprotein by providing a favorable environment and preventing aggregation. They also interact with other chaperones and enzymes to facilitate the formation of disulfide bonds and correct protein folding. This process ensures that the glycoprotein attains its functional conformation before being transported to its destination within the cell.