Which stage occurs immediately after the SRP directs the protein to the ER membrane?

After the signal recognition particle (SRP) directs the nascent protein to the endoplasmic reticulum (ER) membrane, the SRP is released. This stage is crucial because the release of the SRP allows the ribosome to resume translation of the polypeptide chain. The ribosome binds to the translocon in the ER membrane, permitting the growing polypeptide to be translocated into the lumen of the ER as synthesis continues. This process ensures that proteins destined for secretion or for use in the cell membrane are properly inserted into the appropriate cellular compartment.

The subsequent stages involve further processing, such as N-linked glycosylation and the removal of the signal peptide, but these processes occur after the SRP has detached and translation has continued. Therefore, the immediate next step following the binding of the SRP to the ER membrane is indeed the release of the SRP, which is critical for the continuation of protein synthesis and proper protein trafficking.