Protein Targeting: Endoplasmic Reticulum Flashcards
Where is the protein ER signal sequence located?
N-terminus of proteins destined for the ER
When is the ER signal sequence synthesised?
During protein translation
How many amino acids long is the ER signal sequence?
16 - 20
What types of amino acids are ER signal sequences comprised of?
1 or more charged residues and 6-12 hydrophobic residues
What does the Signal Recognition Particle (SRP) do in the targeting of secretory proteins to the ER?
- Binds to the signal sequence of proteins
- Slows elongation of the polypeptide
- Targets polypeptide + ribosome to ER
What is the structure of the Signal Recognition Particle (SRP)?
- Cytosolic ribonucleoprotein (RNA:Protein complex)
- 300 nucleotide RNA + 6 protein subunits
Which protein subunit of the Signal Recognition Particle (SRP) binds to the signal sequence and also GTP?
P54
Which protein subunits of the Signal Recognition Particle (SRP) interacts with the ribosome?
P9 / P14
Where is the SRP Receptor located?
ER membrane
What is the structure of the SRP receptor?
2 subunits (α and β)
Which subunit of the SRP receptor binds GTP?
α subunit
What promotes the interaction between the SRP and the SRP receptor?
Binding of GTP
What is the Translocon in the ER membrane composed of multiple copies of
Sec 61 complex
TRUE OR FALSE:
Translocation of proteins across the ER membrane is CO-TRANSLATIONAL in Eukaryotes?
True.
Occurs as peptide is being made by ribosome
Which enzyme cleaves off the signal sequence as the protein passes through the ER membrane?
Signal peptidase