Intracellular Protein Trafficking (1) Flashcards
What is a signal sequence?
Short sequence at N-terminus
What is a signal patch?
Multiple short sequences - come together with folding
What is the signal sequence for nuclear import?
Lysine and arginine-rich - positive - do not need to be at end of chain
What is the signal sequence for mitochondrial import?
Amphipathic alpha helix
What is the signal sequence for ER import?
Hydrophobic AAs
How do small proteins move into the nucleus?
Diffusion through nuclear pores
How do large proteins move into the nucleus?
Active transport through nuclear pores - via contact with nuclear pore protein complex
What are the nuclear localisation signals?
Signal sequence - positive lysine and arginine residues - do not need to be at end of chain
Signal patch - 2 areas of positive AAs
Which protein does a nuclear pore complex consist of?
Nucleoporins
What is the nuclear import signal?
NLS
What is the nuclear export signal?
Double leucine
Which protein regulates the directionality of protein transport?
Ran
What is Ran-GEF and where is it located?
Exchanges GDP for GTP
In nucleus
What is Ran-GAP and where is it located?
Hydrolyses Ran-GTP
In cytosol
Is protein tranlocated into nucleus folded?
Yes
Is protein translocated into mitochondria folded?
No
Where in the mitochondria does translocation occur?
Where inner and outer membranes close together
Which enzyme cleaves the signal sequence in the mitochondrial matrix?
Signal peptidase
What keeps the protein unfolded for mitochondrial translocation?
Cytosolic Hsp70 (ATPase)
What prevents the protein moving back through TIM and pulls it into mitochondrion?
Mitochondrial Hsp70 (ATPase)
What fold the protein in the mitochondrial matrix?
Hsp60
What keeps the protein unfolded in the mitochondrial intermembrane space?
Chaperones
Where is the SAM complex located?
Outer mitochondrial membrane
Where is the OXA complex located?
Inner mitochondrial membrane
