What occurs after the protein reaches the ER membrane and binds to the SRP receptor?

What occurs after the protein reaches the ER membrane and binds to the SRP receptor?

• A. The ribosome dissociates from the mRNA
• B. The sec61 channel allows translocation of polypeptides
• C. Chaperones assist in proper folding
• D. N-linked glycosylation begins

Answer: (B)

When a protein reaches the endoplasmic reticulum (ER) membrane and binds to the signal recognition particle (SRP) receptor, the next crucial step is the translocation of the polypeptide across the membrane. This process is facilitated by the Sec61 channel, which serves as a translocon. Once the ribosome is docked at the SRP receptor, the signal sequence of the nascent polypeptide engages with the translocon, allowing the growing polypeptide chain to be threaded into the lumen of the ER as translation continues. This seamless integration of translation and translocation is essential for the proper functioning of many proteins that are either secreted from the cell or integrated into cellular membranes. The role of the Sec61 channel is pivotal because it creates an aqueous pore through which the polypeptide can pass, ensuring that the protein's signal sequence is correctly processed for its eventual destination, whether that is within the ER, beyond to the Golgi, or toward secretion outside the cell. Understanding this step is fundamental in the broader context of protein trafficking, as it highlights how the ER acts as a gateway for proteins destined for various cellular locations. The initiation of N-linked glycosylation and the assistance of ch

When a protein reaches the endoplasmic reticulum (ER) membrane and binds to the signal recognition particle (SRP) receptor, the next crucial step is the translocation of the polypeptide across the membrane. This process is facilitated by the Sec61 channel, which serves as a translocon.

Once the ribosome is docked at the SRP receptor, the signal sequence of the nascent polypeptide engages with the translocon, allowing the growing polypeptide chain to be threaded into the lumen of the ER as translation continues. This seamless integration of translation and translocation is essential for the proper functioning of many proteins that are either secreted from the cell or integrated into cellular membranes.

The role of the Sec61 channel is pivotal because it creates an aqueous pore through which the polypeptide can pass, ensuring that the protein's signal sequence is correctly processed for its eventual destination, whether that is within the ER, beyond to the Golgi, or toward secretion outside the cell.

Understanding this step is fundamental in the broader context of protein trafficking, as it highlights how the ER acts as a gateway for proteins destined for various cellular locations. The initiation of N-linked glycosylation and the assistance of ch