Lecture 7 Flashcards
Other than NLS, what is required for nuclear transport?
Cytosolic proteins (in lysate)
What is the function of Digitonin?
Makes plasma membrane permeable
What maintains the direction of nuclear import?
G protein (Ran) gradient
What maintains the Ran gradient?
- Ran-GAP
- Ran-GEF
What are the 2 conformations of Ran?
- Ran-GDP
- Ran-GTP
What is Ran-GEF? Function? Location?
- Guanine Exchange Factor
- Converts Ran-GDP to Ran-GTP
- Attached to chromatin in nucleus
What is Ran-GAP? Function? Location?
- Guanine Activating Protein
- Converts Ran-GTP to Ran-GDP
- In cytosol
Describe the process of nuclear import.
- Cargo w/ NLS sequence binds to importin
- Cargo complex goes through nuclear pore complex into nucleus
- Ran-GEF converts Ran-GDP to Ran-GTP
- Ran-GTP kicks off cargo and binds to importin
- Ran-GTP/importin complex exported to cytoplasm through NPC
- Ran-GAP converts Ran-GTP to Ran-GDP
- Ran-GDP goes back in to nucleus and importin is released in the cytoplasm
Describe the process of nuclear export.
- Ran-GEF converts Ran-GDP to Ran-GTP
- Ran-GTP binds to exportin and cargo
- Cargo complex exported into cytoplasm
- Ran-GAP converts Ran-GTP to Ran-GDP
- Cargo is released into cytoplasm; exportin and Ran-GDP go back into the nucleus
What sequence(s) must proteins have in order to be exported from the nucleus?
NES and NLS (b/c it had to get in in the first place)
What AA is NES rich in?
Leucine (L)
During nuclear export, what provides the NES?
Exportin
What happens when NF-AT is phosphorylated? Dephosphorylated?
- Phosphorylated = exposed nuclear export signal –> in cytoplasm
- Dephosphorylated = exposes nuclear import signal –> goes to nucleus
What dephosphorylates NF-AT?
Calcineurin (protein phosphatase)
What is required before proteins go to the mitochondria?
Must be post-translational (completed synthesis in the cytoplasm)
