Parts of N - Glycosylation
- 2 NAG
- 9 Mannose
- 3 Glucose
Core segment of N Glycocylation
- Dolichol phosphate
- Embedded in the ER membrane
Steps of N - Glycosylation
- Core segment assembled on lipid carrier called dolichol phosphate which is embedded in the ER
- Sugars are addes to dolichol phosphate one by one by glycotransferases
- 2 NAG 9 Mannose 3 Glucose: Total 14 sugars
- Oligosacchryl tranferase helps it bind to aspargine
Quality control of Glycosylation
- Gradual removal of CHO
- Binds to molecular chaperone : Calnexin
- Glucosidase 2 removes the final terminal glucose
- Glycoprotein folding then assessed by a conformation sensing enzyme called UGGT protein
Cis face of golgi
Faces ER
Trans face of golgi
Opposite side of stack
Cis Golgi network
- Sorting station
- Back to ER
- Go to trans golgi
Trans golgi netwoek
Packaging to different organelles
Vesicular transport model
Model of transport from cis to trans
Cisternal maturation model
Cisternae moves as it matures from cis or trans
Golgi cisternae move in _____ fahsion
Anterograde
Vesicles move in a ____ fahsion
Retrograde
COP 2
Move forward
ER to Golgi
COP 1
Backward
Trans to cis to ER
Clathrin
TGN - Endosomes and lysosomes
COP 2 - Coated Vesicles
- ER exit sites
- EX export signals
- Proteins transported by COP 2 coated vesicles
What are the proteins transported by COP2 Coated vesicles
- Glycotransferases to Golgi
- Vesicle docking proteins
- Cargo selecting proteins
Clathrin Coated Vesicles
- Trans Golgi network to endosomes and lysosomes
Sar 1
G protein required
- Requires COP 2 proteins and Cargo receptors
- It is all coated
Where do COP 2 coated vesicles bud
ER exist sites (ERES)
Steps of COP2
- Sar protein binds to GDP and binds to ER membrane
- Induces a wedge
- Sec 23 and 24 forms a complex and binds with cargo: Increase the curvature of the vesicle
- Sec 31 increase the curvature furthur more
Two layers of Transport Vesicles
- Outer scafold
- Inner layer
Structure of clatherin
- Outer scaffold structures
- ## Three legged complexes
2 mechanisms of maintainace of membrane composition
- Retention
- Retrieval
