Summary
A ribonucleoprotein that guides ribosomes making secretory proteins to the endoplasmic reticulum membrane.
In depth
When a ribosome starts translating a protein with an N-terminal signal sequence, SRP binds the sequence, pauses translation and docks the complex at the SRP receptor on the ER, where the ribosome is passed to a translocon. Translation then resumes and the chain threads into the ER lumen.
The signal peptide is often cut off by signal peptidase.
SRP is a ribonucleoprotein, made of a 7S RNA and six proteins, that binds hydrophobic signal sequences of about 15 to 30 amino acids. Proteins with such signals are destined for secretion, the plasma membrane, lysosomes or the ER and Golgi; the signal serves as a ticket. Without a signal the ribosome stays free in the cytosol.
Membrane proteins have stop-transfer sequences that stay in the bilayer and give their orientation. Insulin, antibodies and digestive enzymes are all made via this pathway; Blobel received the 1999 Nobel Prize for the signal hypothesis.
Key idea: protein location is encoded in the amino acid sequence, and the cell reads this as a postal address.
Frequently asked questions
What is Signal Recognition Particle?
A ribonucleoprotein that guides ribosomes making secretory proteins to the endoplasmic reticulum membrane.
Which area of biology covers Signal Recognition Particle, and how advanced is it?
Signal Recognition Particle is one of the 52 topics in Cell Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Ribosome, Endoplasmic Reticulum, Vesicle Trafficking.
Why does Signal Recognition Particle matter?
This is how secreted proteins like insulin and membrane proteins are directed to the right place.
What should I learn before Signal Recognition Particle?
Work through the Beginner topics in Cell Biology first, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell, then return to Signal Recognition Particle. Advanced topics assume the Intermediate vocabulary.
What topics are related to Signal Recognition Particle?
The closest topics to Signal Recognition Particle are Ribosome, Endoplasmic Reticulum, Vesicle Trafficking, Cytoplasm. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Signal Recognition Particle?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Signal Recognition Particle. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Signal Recognition Particle different from Ribosome?
Signal Recognition Particle: A ribonucleoprotein that guides ribosomes making secretory proteins to the endoplasmic reticulum membrane. Ribosome: A small particle of RNA and protein that assembles amino acids into polypeptides during translation. Read both side by side and note what each one explains.
How should I study Signal Recognition Particle step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Ribosome and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.