Protein Trafficking Flashcards
What are the three modes of protein trafficking
Describe characteristics of the nucleus
What are the methods to get an image of the NPC
What is transported in and out of the nucleus
What are the key components in nuclear import/export
Ran(which can have GTP or GDP bound)
Karyopherins (importins/exportins)
Cargo (NLS, macromolecules)
Nucleotide exchange factor
Helper proteins
What is the structural bases for importin activity
At are the 4 models which may explain how transport through the NPC works
Elective phase/ hydrogel model
Virtual fate/polymer brush model
Forest model
Reduction of dimensionality model
What is the basic structure of the nucleus
What is the nuclear lamina and what is its role
How are ribosomes transported between the cytosol and nucleus
What is imported and exported into/ out of the nucleus to the cytosol
What are nuclear pore complexes and what is its role
(They are holes in the nuclear envelope)
How do molecules pass through the NPC
What is the role of nuclear localisation signals
NLS is a signal (molecule) that is found on the cargo proteins (which are the proteins that are to be transported)
How is nuclear import initiated (and what is the role of adaptor proteins)
What is the role of import receptors
What is the role of FG-repeats
What does the nuclear export process rely on
How does RanGTPases impose directionality on transport through NPCs
Asymmetric dustribtipn of RanGDP/GTP
Nucleus: High concentration of RanGTP.
Cytoplasm: High concentration of RanGDP
Ran GEF, specifically RCC1, is localized in the nucleus and facilitates the conversion of RanGDP to RanGTP. This is why the nucleus has a high concentration of RanGTP
Ran GAP, which is associated with the cytoplasmic side of the NPC or cytoplasm itself, promotes the hydrolysis of RanGTP to RanGDP. This is why the cytoplasm has a high concentration of RanGDP.
Import receptors (importins) bind to cargo proteins in the cytoplasm where RanGDP is abundant.
The importin-cargo complex translocates through the NPC into the nucleus.
In the nucleus, RanGTP binds to the importin, causing it to release the cargo.
The RanGTP-importin complex then returns to the cytoplasm
Export receptors (exportins) bind to cargo proteins and RanGTP in the nucleus to form a ternary complex.
This complex translocates through the NPC into the cytoplasm.
In the cytoplasm, the high concentration of RanGAP leads to the hydrolysis of RanGTP to RanGDP.
This hydrolysis causes the dissociation of the export complex, releasing the cargo and RanGDP
What is meant by monomeric
Proteins with one polypeptide chain
What is Ran
A GTPase (which is an enzyme which binds to GTP protein and hydrolyses it)
It’s a molecular switch
Can have GTP or GDP bound
What is the role of GTPase activating protein (GAP)
Triggers GTP hydrolysis
Converts Ran-GTP to Ran-GDP
What is the role of guanine exchange factors
Promote exchange of GDP for GTP
So converts Ran-GDP to Ran-GTP
Where is Ran-GAP and Ran-GEF located
Ran-GAP- located in cytosol
Ran-GEF - located in nucleus and is associated with chromatin
Where is Ran-GDP and Ran-GTP mainly found
Ran-GDP mainly found in cytosol
Ran-GTP mainly found in nucleus
Explain the process of nuclear import
How does nuclear export occur
