A newly synthesized protein destined for secretion from the cell contains an N-terminal signal peptide. Which complex recognizes this signal peptide and directs the ribosome to the endoplasmic reticulum?
- A Signal recognition particle (SRP) ✓
- B Clathrin coat
- C COPII vesicle
- D Nuclear localization signal receptor
Correct answer: A. Signal recognition particle (SRP)
Explanation
The signal recognition particle (SRP) binds the N-terminal signal peptide as it emerges from the ribosome during translation. SRP pauses translation and directs the ribosome-nascent chain complex to the SRP receptor on the rough endoplasmic reticulum. Translation then resumes with co-translational translocation into the ER lumen. Clathrin and COPII are involved in vesicular transport, not initial protein targeting.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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