Lecture 11 Flashcards
Cisternae?
Stacks that make up of the golgi
Cis vs Medial vs Trans cisternae?
Cis: found closest to the ER
Medial : found in the middle of the golgi
Trans : closest to PM
Modifications of proteins at golgi?
- N-linked glycosylation
- O-linked glycosylation
Golgi glycosylation is not uniform like that in the ER?
True
Functions of Glycosylation?
- Promotes protein folding
- Protective
- Provides addional modulations to the protein
Glyco code?
Addition of sugars is in a specific order which tells the cell what stage the protein is in
Proprotein Convertases:
Proteins in the ER are made longer and inactive once in the ER proprotein convertase cleaves the protein to make it into its active form
Purpose of converses?
- Long protein easier than putting together a bunch of small proteins
- Inhibitory region may have additional info about folding/trafficking
- MAy not want the protein to be active yet
Ras vs Rabs?
Rabs bind specific effectors whereas Ras can bind anything
Rabs compartment specific?
Rabs are different in each organelle and give compartments identity
As a vesicle buds off from one location it typically contains a Rab that tells them where they came from
Structure of Rabs?
Two prenyl lipid groups attached to their C-termini
Rab-GDP and GDI?
Rab-GDP (inactive), the hydrophobic prenyl groups are folded away and hidden by GDI binding which allows Rab-GDP to be soluble in the cytoplasm
Rab-GDP + GEF?
GEF convert Rab-GDP to Rab-GTP, GDI then dissociates exposing the hydrophobic prenyl groups and the Rab now inserts into the membrane of a specific organelle
Rab functions?
- Vesicle targeting
- Making sure the right proteins are in the vesicle
- Once the coat has been removed Rabs connect to motor proteins for transport(tethers/SNARES)
Tethers?
Stick out from organelles, effector of Rabs is typically a tether. Tether helps bring the vesicle to the organelle
SNAREs?
Fusion proteins that force the vesicle right up next to the PM and force it to fuse
Two Types of tethers?
- Coiled-coil(simple, golgi)
- Multisubunit tehter(complex, many different proteins)
Coiled-coil tether structure?
Dimers with two alpha-helices that stay assembled and stick out from an organelle
Golgin?
Tether that sticks out from the golgi stacks
-Anchored by Rab
-Contains domains that bind Rabs
Multisubunit tether for transport from ER to golgi?
TRAPPI
-found at the golgi
-Is a GEF that can activate Rab
