Sorting 1 Flashcards
Proteins that get secreted have a secretion signal that is located at what ?
The N-termini
What do we do as soon as protein starts to emerge and then where does it go ?
We stop making proteins and then everything will go to the ER if it contains a secretion signal
What is the secretion signal that has emerged from a ribosome bound by ?
SRP
What is the first job of SRP is responsible for ?
Halting translation
What is the second job that SRP is responsible for ?
It binds to the SRP receptor
What is a translocon ?
A channel in the ER membrane
Where does the secretion signal sequence always get stuck ?
The translocon
Where does translation drive a polypeptide that has a secretion signal sequence to go ?
Drive it to go to the ER lumen (Through the translocon)
Where is the signal peptidase anchored ?
The translocon
The secretion signal sequence that is anchored in the translocon is cleaved by what ?
Cleaved by Signal peptidase
Where is the protein released after is has been cleaved by the signal peptidase ?
The ER Lumen
Why do we call a protein a Transmembrane Protein ?
Transmembrane proteins cross the membrane
Where does a stop transfer sequence always get stuck ?
In the translocon
What does the Stop Transfer Sequence do ?
As the name suggests, it stops proteins through the translocon (cannot be cleaved)
What is a Multi Pass transmembrane protein ?
A protein that goes through the membrane a multiple number of times
What must happen to proteins in order for them to do their job correctly ?
They must be folded correctly
Are proteins in the translocon folded or are they in the form of a line ?
Form of a line
Is the ER lumen the same as the cytoplasm or is it different ?
It is different because there can be different environments
What does the ER have that helps proteins fold correctly ?
The ER has specific enzymes that help folding which are called chaperone
What type of environment does the ER have ?
It has an oxidizing environment
What type of environment does cytoplasm have ?
A reducing environment
What are disulfide bonds ?
Bonds that are between sulfurs
What do all proteins that end up in the ER become ?
They become glycosylated
What do sugars act as ?
They act as shipping labels and inspection labels
Why is it important that sugars act as shipping labels ?
So we know where a protein is eventually going to go
What do some proteins also require be added to them
Some will need lipids because it they be in the membrane
How is quality control in the ER maintained ?
We use a protein called Calreticulin and folding sensors
What does Calriticulum do ?
Helps things fold correctly
What does the folding sensor do ?
Gives the green light a protein is ready to be sent. If not it will be sent back to be remolded correctly. Sometimes if a protein is too messed up to be refolded it will disregard the protein entirely.
What do we keep on stand by if a protein is not folded correctly ?
Chaperones
What is most likely the issue that is happening if all the sudden we have a gene that is consistently sending out bad proteins ?
A mutated gene
How much help do proteins need in order to do their job ?
Not a lot, but some help here and there
What does sequester mean ?
Keeping chaperones seperated until they are needed.
Is the stop transfer sequence bounded by SRP ?
What must occur for a protein to get out of the translocon and into the ER Lumen ?
It must be cleaved
What do we modify in the ER and what might some of them end up with ? What do they always have ?
We modify proteins in the ER. WIll sometimes end up with a lipid, but will always have a sugar
What will the protein attach to if it has a lipid ?
The membrane
What do sugars act as ?
Shopping label and inspection label
WHat do proteins have to do in order to work correctly ?
Must fold correctly
What is the addition of sugars called ?
Glycosylation
What are the results that happen when quality crontrol in the ER is happening ?
- It’s ready to go
- It’s not ready to go
- It’s so bad that we send it ubiquination ?
What is the response that happens when we have a mutated gene ?
TO shut down
What is a more nuclear option when there is a mutation ?
Program cell death. Basically killing ourselves
Why do we have a smooth ER ?
- It is essentially responsible for making our phospholipids
- Makes all the membranes in the cells
Where are phospholipids made ?
The cytosolic face of the ER
What must happen if we only make phospholipids on one side of the ER ?
We have to make it on both sides so we move some of them to the other side
What is an example of a protein that should stay in the ER ?
Calreticulin
What will a protein have if it is meant to be in the ER ?
It will have an ER retention sequence.
What is the place called where we sort proteins ?
ERGIC (ER-Golgi-Intermediate Complex)
What is the ER-GIC ?
A recycling facility for proteins
WHat is similar between a secretion signal sequence and a stop signal sequence.
They both get stick translocon
What is different between a Stop signal sequence and a secretion signal sequence
Stop can be cleaved and signal can. SRP isn’t bounded to the stop and srp is bounded to the secretion
What must occur for a protein to get out of the translocon and into the ER membrane
It must move laterally out of the translocon
How do we flip phoslipiids from one side of the er membrane to the other.
The enzyme flipase
Er retention sequence means ?
A certain sequnce of amino acids
