Lecture 6 Flashcards
What is the purpose of COP II vesicles?
ER to golgi transport (anterograde)
What is the purpose of COP I vesicles?
Goli to ER transport (retrograde)
What is the purpose of clatherin coated vesicles?
Transport from the cell membrane to the trans golgi or to the late endosome
What are the two types of proteins that make up a snare complex?
vSnares and tSnares
What are the basic steps in vesicle transport?
Recruitment of coating protein driving the budding process Pinching off of bud loss of coating proteins Snare Complex interactions Transport driven via microtubules
What causes the COP II coat to be recruited in the ER?
Sec 12 in the vesicle membrane binds sar1, this results in GTP hydrolysis by Sar1 allowing it to act as an anchor recruiting the sec 23/24 proteins which forms the COP II coat
What causes loss of the COP II coat?
Sar12 rebinds GTP resulting in a conformational change which releases its ‘anchor’ to the cell membrane
What is the purpose of retrograde transport?
To return mis-sorted proteins required for ER function to the ER from the golgi
What sequence does retrograde transport use to make sure that the correct proteins are returned to the ER?
The KDEL sequence
What is the KDEL sequence?
Lys-Asp-Glu-Leu
What causes proteins to bind to the KDEL receptor in the golgi but not in the ER?
The higher pH of the ER
What is the most likely method of proteins being taken into COP II vesicles for anterograde transport?
Bulk Flow
What recruits the COP I coat for retrograde transport?
The KDEL sequence when it binds to and ER protein
What is the sorting signal on proteins for the formation of COP I transport?
Lys-Lys-X-X
What is the sorting signal on proteins for COP II transport for the distal secretory pathway?
Asp-X-Glu
How do golgi bodis move from cis golgi to maedial and then trans golgi?
Through cisternal maturation, NOT vesicle transport
What GTPase leads to formation of the COP I coat?
Arf
What process creates the signal that targets proteins into the lysosome?
Glycosylation
What amino acid are the sugars in glycosylation addded to?
Asparagine
What sequence signals the ER to add sugars to a protein?
Asn-X-Ser/Thr
What is the enzyme that adds the sugars to the protein in asparagine?
oligosaccharyl transferase
What is the initial sugar added to proteins that undergo glycosylation?
(Glc)3(Man)9(GlcNAc)2
What occurs to the sugar added to proteins?
It is trimmed to (Man)8 core which signals transfer to the golgi
How is the sugar modified in the cis golgi to be targeted to the lysosome?
It is changed to a mannose-6-Phosphate
