Session 10 (work group)-Protein Targeting Signals Flashcards Preview

Semester 1-MCBG > Session 10 (work group)-Protein Targeting Signals > Flashcards

Flashcards in Session 10 (work group)-Protein Targeting Signals Deck (12):
1

What is the nature of the signal to the ER?

Signal sequence (recognised by SRP during translation)

2

What is the nature of the signal to the nucleus?

NLS=nuclear localising signal
Basic (Arg/Lys)
May be multipartite (having many divisions)

3

What is the nature of the signal to the mitochondria?

Amphipathic signal for initial targeting to the matrix

4

What is the nature of the signal to the lysosomes?

Post-translational addition of mannose-6-phosphate

5

What is the nature of the signal for retention in the ER?

KDEL (Lys-Asp-Glu-Leu)

6

Where is the signal's location within the primary sequence in the ER?

N-terminus

7

What is the signal's location within the primary sequence in the mitochondria?

N-terminus (may also be internal "stop transfer"=hydrophobic)

8

Location of signal within primary sequence for retention in ER?

C-terminus

9

Folded or unfolded during transfer:
1. To ER
2. To nucleus
3. To mitochondria
4. To lysosomes
5. Retention in ER

1. Unfolded
2. Folded
3. Held partially unfolded by chaperones
4. Folded
5. Folded

10

What are the specialist proteins involved:
1. To ER
2. To nucleus
3. To mitochondria
4. To lysosomes
5. Retention to ER

1. Signal recognition protein (SRP), SRP receptor
2. Importin recognises NLS and mediates transport; RanGTP displaces it in nucleus and drives out export cargo.
3. Mitochondrial-import stimulating factor ((MSF), Tom and Tim channel complex
4. M-6-P receptor in trans-Golgi
5. KDEL receptor in cis-Golgi

11

Signal retained or cleaved:
1. To ER
2. To nucleus
3. To mitochondria
4. To lysosomes
5. Retention in ER

1. Cleaved by signal peptidase
2. Retained
3. Cleaved
4. Phosphate removed by phosphatase
5. Retained

12

Requires energy?
1. To ER
2. To nucleus
3. To mitochondria
4. To lysosomes
5. Retention in ER

1. Yes-hydrolysis of GTP by SRP
2. Yes-hydrolysis of GTP
3. Yes-ATP hydrolysis by mHsp70 drives translocation; MSF uses ATP to keep some precursors unfolded
4. Yes-phosphotransferase requires ATP (but not direct)
5. No-involves binding and release dependent on pH