Week 10 - Protein Sorting Flashcards
What is the Endoplasmic reticulum
A vast network of tubules which extend throughout cytoplasm
What are the two types of endoplasmic reticulum
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
What are the functions of the SER
Lipid synthesis, hormone synthesis, Ca storage and detoxification
What are the functions of the RER
Site of protein synthesis and processing for transmembrane proteins as well as proteins secreted from the cell
Describe co translational translocation
Importing of proteins during translation, where no chaperone protein required due to the protein remaining in primary sequence as its attached to the ribosome as it enters ER
What conditions are needed for co translational translocation to occur
Recognised by Signal recognition particle
Recognised by ER and embedded within ER membrane
Describe the steps of recognition by an SRP
Signal sequence recognised on the N terminal of polypeptide, binds to that signal sequence and the ribosome.
What happens to the ribosome after translation
It’s released back into the free ribosome pool
What happens to the mRNA after translation
It is degraded
What are the two fates of a protein after it is made
Exocytosis via ER lumen
Become a membrane protein by being embedded in the ER membrane
What are the two ways a protein can be modified in the ER
Folding into its 3D conformation
Glycolysation
What is glycolysation
The addition of a sugar to a protein
What three things are glycolysation important for
Quality control
Recognition
Protection
How does glycolysation work
A precursor oligosaccharide (14 sugars) added to N terminus of protein as asparagine side chain during protein synthesis
How does quality control during glycolysation work
3 glucose removed from oligosaccharide, if folded, protein exits ER, if not glucosyl transferase + 1 glucose back on and then protein binds to calnexin to prevent agreggation, glucosyl transferase decides if protein is correctly folded
