2.4 Intracellular compartments and protein sorting 2 Flashcards
Pertaining to Nucleus Cytosol, fibrils interact with what?
Import proteins
Pertaining to Nucleus Cytosol, what does the nuclear basket do?Where is it located?
Is inside the nucleus. Tethers active genes to NPC. Regulated transport
Dealing with nuclear import, What is the NLS?
Sorting signal with + AAs. Usually internal.
What recognizes the NLS?
NIR or importins.
What do Importins do?
ferry cargo into nucleus.
Pertaining to nuclear export, what is the NES?
Nuclear export sorting sequences that contain + and - AAs.
What recognizes the NES?
NER or exportins.
What do exportins do?
Ferry cargo into cytosol.
What is shuttling pertaining to nucleus
We can go in and out both ways. Shuttle proteins back and forth.
pertaining to shuttling, what is a powerful regulatory strategy?
compartmentalization
Regulation of recognized signal sequence is by what 3 things?
Phosphorylation, proteolysis, and inhibitor proteins
What are karyopherins?
Importins and exportins.
What requires energy to pass through the nuclear pore? What energy does it use?
Anything large. GTP
What is Ran?
GTPase
Where is Ran-GAP only found? What does it do?
Cytoplasm. Catalyzes the removal of phosphate.
Where is Ran-GEF only found? What does it do?
In nucleus. Exchanges GDP to GTP.
How doe this GTPase system work with exporting?
Nucleus to cytosol. Ran-GTP in nucleus, associates with Exportin. Once in cytosol, Ran-GAP (hydrolysis of GTP by removing Phosphate) releases cargo.
How doe this GTPase system work with importing?
Cytosol to nucleus. Ran-GTP releases the cargo, that association initiates recycling of importin back to cytosol. Once importin in cytosol it releases Ran-GDP.
Pertaining to cytosol –> mitochondria transport, how many compartments are there?
- Outer membrane (OM). Intermembrane (IMS). Inner membrane (IM) and Matrix.
What complexes are found in the OM?
TOM, SAM, MIM
What do Hsp70/Hsp40 do?
They are cystolic chaperone proteins that keep proteins unfolded.
What does TOM do?
To get though the OM you must go through TOM.
What does SAM do?
Inserts Beta Barrel proteins in the OM.
What does MIM do?
Inserts alpha helical proteins in the OM.
Where are the sorting signals that SAM inserts located? Does SAM cleave the signal once inserted?
Internal. No
Where are the sorting signals that MIM inserts located? Does MIM cleave the signal once inserted?
N terminal. No
Which does a protein need to go through if it needs to get through multiple times?
MIM
What complexes are found in the IMS?
MIA and small TIM proteins.
What is MIA?
Performs own function. Redox reactions important for mitochondria. Sorting seq will be very cysteine rich
What are small TIM proteins?
chaperones in the IMS
What complexes are in the IM?
TIM 23, TIM 22, OXA
What does TIM 23 do?
Inserts the most proteins into the IM but cutting off their sorting sequence.
What does TIM 22 do?
Inserts some proteins into the IM. Inserts TIM 23. Doesnt remove sorting seq.
What does OXA do?
Exports from matrix to the inner membrane
What complexes are in the Matrix?
PAM.
What does PAM do?
Helps TIM 23 get proteins into the matrix.
what do we need to get into the matrix?
ATP
What is the energy used for that allows protein to get into the matrix?
On Hsp70, pulls the proteins in the matrix.
Pertaining to cytosol —> ER, what are the two options when inserting into the ER?
Co-translational insertion and post translational insertion
Where does co translational insertion happen?
On R ER.
Where does post translational insertion happen?
Happens when translation occurs on free ribosomes.
For co translational, what are the cytosolic chaperones?
SPR, SR
For post translational, what are the cytosolic chaperones?
Hsp70/40
For co translational what energy is the energy source?
GTP
For post translational what energy is the energy source?
ATP
For co translational, where is the energy used?
SRP recycling, translational elongation
For post translational, where is the energy used?
Bip pulling
What do both co/post translational have in common?
Sorting sequence.
What is the structure, where the co/post translational sorting sequence? Does it get cleaved?
Located at N. 3 parts: N domain (charged). H domain (hydrophobic). C domain (polar). Gets cleaved
How does the SRP work?
Find ribosome, has 2 places where itll bind. At the exit channel (where the signal seq is coming out first) located at the N terminus of the protein. Also covers where the elongation factors enter at the ribosome. So there will be pause on the ribosome. Once bound to our SRP receptor, that is when we release everything. Release that signal seq, so that it can enter into the translocator, our ribosome will stay with our translocator and our SRP and its receptor will be recycled to continue the process
