Describe the structure of Sec61
Trimeric- Alpha, beta and gamma subunits
Dimeric- 1A & 1B subunits
Tetrameric- A, B, C & D subunits
What of the role of Sec 61 in ER transport?
Forms the pore itself
Binds the nascent polypeptide
Folds the nascent polypeptide once it's passed through
Which pore-associated protein interacts with the signal recognition particle?
What is the role of the Sec62/63 complex?
Contains a J domain
Contains a G/F domain
That signals the ATPase domain of Hsp40 in the ER (Bip)
That signals the ATPase domain of Hsp70 in the ER (Bip)
The Bip protein acts as a ratchet, pulling the protein through and preventing it moving backwards
The first Asparagine to enter the ER has what added to it?
The sugar added to the Asparagine is 12 residues long
Once the sugar has been added, what happens?
Glucosidase 1 & 2 remove glucose residues
Fructosidase 1 & 2 remove fructose residues
Galactosidase 1 & 2 remove galactose residues
Once the residues have been removed, the protein is folded by one of which chaperones?
The Cal_ protein doing the folding will be bound to Erp57
What happens after the protein has been folded?
Another glucose is removed
Another fructose is removed
Another galactose is removed
Once the final residue is removed, the protein enters ERAD quality control, in which 2 things can happen
Other than exiting the ER as a correctly folded protein, what can happen after protein folding is complete?
Protein is reglycosylated
Protein has mannose residues removed
Protein has ions added
Protein is degraded
In the case of a misfolding that the ER can correct, what protein is used to signal this?
Glycoprotein Glycosyl Transferase
What proteins remove mannose resiudes of proteins to be degraded?
Which protein leads a misfolded protein out of the ER to be degraded in the protesome?
What is the role of Epr-57?
To make/break disulphide bonds
To cleave Signal Recognition Particle
To bind Calreticulin to the membrane
Calnexin is membrane bound, Calreticulin is not
In Cal_ and Cal_, where on the protein to be folded to they bind?
Lectin domain- an exposed glucose residue
Pectin domain- an exposed Fructose residue
Plectrin domain- an exposed mannose residue
The protein end not bound to the sugar residue binding site is bound to what?