Week 8 Flashcards
T/F:
The nucleus is surrounded by a double membrane that is continuous with the ER
True
The inner nuclear membrane separates the ___ from the ___
Nucleoplasm from the ER lumen
The outer nuclear membrane separates the ___ from the ____
ER lumen from the cytoplasm
Proteins that are destined for the nucleus are bound by what type of proteins?
Bound by carrier proteins
T/F:
Proteins destined for the nucleus are translated on free ribosomes on the ER
False
free ribosomes in the cytoplasm
What is the name of the proteins that make up the nuclear pore complex?
Nucleoporins
What is the membrane portion of the nuclear pore complex attached directly to?
The nuclear lamina
How many long filaments extend from the nuclear pore complex and join to form a nuclear basket?
8
What is found in the centre of the nuclear pore complex?
A matrix of FG repeats in the central channel
What is the role of the hydrophobic FG repeat of the nucleoporin?
Phenelalanine and glycine
Recognise what’s being imported into the nucleus
The mesh is pushed aside and the incoming protein can interact with the residues
What molecular weight of ions and small metabolites can pass through the nuclear pore complex passively?
Ions, small metabolites and proteins of less than 40kDa
What type of residues does the nuclear localization signal (NLS) contain?
Lots of basic residues
What two basic residues are often seen in the NLS?
Lysine and Arginine
T/F:
The NLS signal is required to bring things into the nucleus
True
Which protein initially binds the cargo destined for the nucleus?
Importin
What does the importin molecule interact with in terms of the nuclear pore complex?
It binds to a nucleoporin that contains a short hydrophobic sequence (lots of phe and gly repeats)
T/F:
Interaction with Ran-GDP allows the importin to release the cargo within the nucleus
False
Interaction with Ran-GTP
Causes a conformational change and the cargo can be released
How does Ran-GTP then get recycled so it can be used again?
Exchanges GDP for GTP in the prescence of the Ran-guanine exchange factor (Ran-GEF) inside the nucleus
Interaction with Ran-GTPase activating protein (Ran-GAP) in the cytoplasm allows the RAN to hydrolyse the GTP and be ready for another cycle
What identifies proteins as proteins needed to be EXPORTED from the nucleus?
They contain a leucine rich export signal
It has a specific spacing of hydrophobic residues
T/F:
Proteins to be imported into the nucleus are positively charged
True
Importin recognises basic residues
T/F:
Proteins to be exported from the nucleus have hydrophobic residues in their sequence
True
Which two molecules does the cargo protein needed to be exported out of the nucleus interact with?
Ran-GTP and exportin
They form a triple complex
How is Ran-GTP converted into Ran-GDP?
Interacts with GAP to become Ran-GDP
Causes a conformation change and the cargo is released
Increase in blood glucose levels causes what?
Stimulates pancreatic beta cells to secrete insulin
T/F:
When insulin binds to its receptor, two protein kinase b dependent and independent pathways take place at the same time
True
When insulin binds to its receptors, what are the two main things that occur next at the same time?
GLUT4 is translocated to the plasma membrane to collect the glucose
Adipocytes differentiate and have the ability to store glucose
T/F:
Insulin is one chain
False
Two chains with cystine bonds
What cell trigger allows for vesicles containing insulin to be released from the cell?
Potassium leaves and calcium enters
T/F:
Glucose being turned into pyruvate in the cell causes the potassium channels to remove potassium from the cell and creates an action potential and therefore calcium fluxes in
True
T/F:
When insulin levels drop, glut4 receptors will be found on the plasma membrane
False
They will be found in vesicles within the cell waiting for blood glucose levels and insulin levels to increase
What is the role of the activated proteases in terms of Glut4?
They break up TUG into fragments which allows Kinesin to move the vesicle along the microtubule
When insulin binds to the extracellular domain of the insulin receptor, what part of the receptor becomes activated?
Catalytic domain inside the cell
When the catalytic domain of the insulin receptor becomes activated, what does it do?
one receptor phosphorylates Tyr resides on the other receptor
