A newly synthesized secretory protein emerges from the ribosome bearing an N-terminal hydrophobic signal peptide. Which factor binds this peptide and directs the ribosome to the endoplasmic reticulum membrane?
- A Eukaryotic release factor eRF1
- B Signal recognition particle (SRP) ✓
- C Elongation factor 2 (EF-2/eEF2)
- D Signal peptidase complex
Correct answer: B. Signal recognition particle (SRP)
Explanation
The signal recognition particle recognizes the emerging signal peptide as it exits the ribosome, pauses translation, and docks the complex onto an SRP receptor on the rough ER membrane. Translation then resumes through the Sec61 translocon, and signal peptidase later cleaves the peptide inside the lumen. eRF1 mediates termination, EF-2 drives translocation, and signal peptidase acts only after ER docking, so none of these can perform the initial targeting step.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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