Intracellular Protein Trafficking (2) Flashcards
Define glycosylation
Addition of sugar to protein/lipid
Which translocon is involved in cotranslational tranlocation into the ER?
Sec61 complex
What is the role of chaperones in the ER lumen?
Fold protein
Where does N-linked glycosylation occur and describe the process
ER
On asparagine of N-X-S/N-X-T sequence
Using oligosaccharyl transferase -n binds to Sec61, asparagine, and ribosome
How does glycosylation affect a protein?
Causes folding - increases stability - involved in cell adhesion
What marks incorrectly-folded proteins for degradation?
Chaperones
What are the signals for directing proteins from the ER to the correct organelles?
AA sequences
Protein modifications - glycosylation, ubiquitination, lipid modifications
How do vesicles contain the correct soluble cargo protein?
Cargo-receptor proteins face into vesicle
Name the main cargo-receptor proteins
COPI, COPII, clathrin (and adaptor proteins)
Which transport step is COPII involved in?
ER to cis-Golgi
What does COPII consist of?
Sec proteins
Which GTPase is associated with COPII and what is its role?
SarI-GTPase
For assembly and disassembly of coat
What are the overall characteristics of COPII coats?
Selective and structural
Which transport step is COPI involved in?
Cis-Golgi to ER
Later to earlier Golgi cisternae
What does COPI consist of?
Coatomers
Which GTPase is associated with COPI and what is its role?
Arf-GTPase
For assembly and disassembly of coat
What are the overall characteristics of COPI coats?
Selective and structural
What are the overall characteristics of clathrin and adaptor protein coats?
Clathrin - structural
Adaptor proteins - selective
Which pathway is AP1 adaptor protein required for?
Trans-Golgi to endosome
Which pathway is GGA adaptor protein required for?
Trans-Golgi to endosome
Which pathway is AP2 adaptor protein required for?
Plasma membrane to endosome
Which pathway is AP3 adaptor protein required for?
Golgi to lysosome
Which GTPase is associated with clathrin and what is its role?
ARF-GTPase
For assembly
Hsp70 needed for uncoating
