Question

Using the techniques of genetic engineering, you design a protein you want to accumulate within the ER of yeast cells. To accomplish this goal, you need to

A) do nothing; all proteins go through the ER.
B) incorporate appropriate mannose-6-phosphate groups.
C) incorporate the appropriate DNA sequence(s) to create signal sequences in the mature peptide.
D) incorporate radioactive amino acids into the protein.
E) remove the N-formyl group located at the N-terminus of the polypeptide.

Answer 1

Ensure that a designed protein accumulates in the ER of yeast cells, incorporate an N-terminal signal sequence into the protein's DNA sequence. This sequence directs the protein to and through the ER membrane for proper localization and modification. The correct answer is option C.

Step-by-step explanation:

The question asks about how to ensure that a designed protein accumulates within the endoplasmic reticulum (ER) of yeast cells using genetic engineering. To achieve this, the appropriate action would be to incorporate the appropriate DNA sequence(s) that result in signal sequences on the mature peptide (Option C). This N-terminal signal sequence is necessary because it directs the ribosome to the ER membrane, where the growing polypeptide is translocated into the ER lumen. Once inside the ER, the protein will undergo post-translational modifications such as core glycosylation.

All proteins do not naturally go through the ER; thus, option A is incorrect. Mannose-6-phosphate groups (Option B) are involved in targeting proteins to lysosomes, not the ER. Radioactive amino acids (Option D) would be used to trace a protein, not to affect its localization. Removing the N-formyl group (Option E) is applicable only to prokaryotic protein synthesis and is irrelevant to the targeting of proteins within eukaryotic cells like yeast.

The correct sequence of events for the incorporation of a protein within a cell includes: synthesis of the protein on the ribosome, modification in the ER, tagging in the Golgi apparatus, and distribution via a vesicle to the final destination.